diff --git a/src/OpenFeature/Model/FlagEvaluationDetails.cs b/src/OpenFeature/Model/FlagEvaluationDetails.cs
index 9af2f4bf..28c83e55 100644
--- a/src/OpenFeature/Model/FlagEvaluationDetails.cs
+++ b/src/OpenFeature/Model/FlagEvaluationDetails.cs
@@ -2,74 +2,74 @@
 
 namespace OpenFeature.Model
 {
-    /// <summary>
-    /// The contract returned to the caller that describes the result of the flag evaluation process.
-    /// </summary>
-    /// <typeparam name="T">Flag value type</typeparam>
-    /// <seealso href="https://github.com/open-feature/spec/blob/v0.7.0/specification/types.md#evaluation-details"/>
-    public sealed class FlagEvaluationDetails<T>
-    {
         /// <summary>
-        /// Feature flag evaluated value
+        /// The contract returned to the caller that describes the result of the flag evaluation process.
         /// </summary>
-        public T Value { get; }
+        /// <typeparam name="T">Flag value type</typeparam>
+        /// <seealso href="https://github.com/open-feature/spec/blob/v0.7.0/specification/types.md#evaluation-details"/>
+        public sealed class FlagEvaluationDetails<T>
+        {
+                /// <summary>
+                /// Feature flag evaluated value
+                /// </summary>
+                public T Value { get; }
 
-        /// <summary>
-        /// Feature flag key
-        /// </summary>
-        public string FlagKey { get; }
+                /// <summary>
+                /// Feature flag key
+                /// </summary>
+                public string FlagKey { get; }
 
-        /// <summary>
-        /// Error that occurred during evaluation
-        /// </summary>
-        public ErrorType ErrorType { get; }
+                /// <summary>
+                /// Error that occurred during evaluation
+                /// </summary>
+                public ErrorType ErrorType { get; }
 
-        /// <summary>
-        /// Message containing additional details about an error.
-        /// <para>
-        /// Will be <see langword="null" /> if there is no error or if the provider didn't provide any additional error
-        /// details.
-        /// </para>
-        /// </summary>
-        public string? ErrorMessage { get; }
+                /// <summary>
+                /// Message containing additional details about an error.
+                /// <para>
+                /// Will be <see langword="null" /> if there is no error or if the provider didn't provide any additional error
+                /// details.
+                /// </para>
+                /// </summary>
+                public string? ErrorMessage { get; }
 
-        /// <summary>
-        /// Describes the reason for the outcome of the evaluation process
-        /// </summary>
-        public string? Reason { get; }
+                /// <summary>
+                /// Describes the reason for the outcome of the evaluation process
+                /// </summary>
+                public string? Reason { get; }
 
-        /// <summary>
-        /// A variant is a semantic identifier for a value. This allows for referral to particular values without
-        /// necessarily including the value itself, which may be quite prohibitively large or otherwise unsuitable
-        /// in some cases.
-        /// </summary>
-        public string? Variant { get; }
+                /// <summary>
+                /// A variant is a semantic identifier for a value. This allows for referral to particular values without
+                /// necessarily including the value itself, which may be quite prohibitively large or otherwise unsuitable
+                /// in some cases.
+                /// </summary>
+                public string? Variant { get; }
 
-        /// <summary>
-        /// A structure which supports definition of arbitrary properties, with keys of type string, and values of type boolean, string, or number.
-        /// </summary>
-        public FlagMetadata? FlagMetadata { get; }
+                /// <summary>
+                /// A structure which supports definition of arbitrary properties, with keys of type string, and values of type boolean, string, or number.
+                /// </summary>
+                public ImmutableMetadata? FlagMetadata { get; }
 
-        /// <summary>
-        /// Initializes a new instance of the <see cref="FlagEvaluationDetails{T}"/> class.
-        /// </summary>
-        /// <param name="flagKey">Feature flag key</param>
-        /// <param name="value">Evaluated value</param>
-        /// <param name="errorType">Error</param>
-        /// <param name="reason">Reason</param>
-        /// <param name="variant">Variant</param>
-        /// <param name="errorMessage">Error message</param>
-        /// <param name="flagMetadata">Flag metadata</param>
-        public FlagEvaluationDetails(string flagKey, T value, ErrorType errorType, string? reason, string? variant,
-            string? errorMessage = null, FlagMetadata? flagMetadata = null)
-        {
-            this.Value = value;
-            this.FlagKey = flagKey;
-            this.ErrorType = errorType;
-            this.Reason = reason;
-            this.Variant = variant;
-            this.ErrorMessage = errorMessage;
-            this.FlagMetadata = flagMetadata;
+                /// <summary>
+                /// Initializes a new instance of the <see cref="FlagEvaluationDetails{T}"/> class.
+                /// </summary>
+                /// <param name="flagKey">Feature flag key</param>
+                /// <param name="value">Evaluated value</param>
+                /// <param name="errorType">Error</param>
+                /// <param name="reason">Reason</param>
+                /// <param name="variant">Variant</param>
+                /// <param name="errorMessage">Error message</param>
+                /// <param name="flagMetadata">Flag metadata</param>
+                public FlagEvaluationDetails(string flagKey, T value, ErrorType errorType, string? reason, string? variant,
+                    string? errorMessage = null, ImmutableMetadata? flagMetadata = null)
+                {
+                        this.Value = value;
+                        this.FlagKey = flagKey;
+                        this.ErrorType = errorType;
+                        this.Reason = reason;
+                        this.Variant = variant;
+                        this.ErrorMessage = errorMessage;
+                        this.FlagMetadata = flagMetadata;
+                }
         }
-    }
 }
diff --git a/src/OpenFeature/Model/FlagMetadata.cs b/src/OpenFeature/Model/FlagMetadata.cs
deleted file mode 100644
index 0fddbdd3..00000000
--- a/src/OpenFeature/Model/FlagMetadata.cs
+++ /dev/null
@@ -1,25 +0,0 @@
-using System.Collections.Generic;
-
-namespace OpenFeature.Model;
-
-/// <summary>
-/// Represents the metadata associated with a feature flag.
-/// </summary>
-/// <seealso href="https://github.com/open-feature/spec/blob/v0.7.0/specification/types.md#flag-metadata"/>
-public sealed class FlagMetadata : BaseMetadata
-{
-    /// <summary>
-    /// Constructor for the <see cref="BaseMetadata"/> class.
-    /// </summary>
-    public FlagMetadata() : this([])
-    {
-    }
-
-    /// <summary>
-    /// Constructor for the <see cref="BaseMetadata"/> class.
-    /// </summary>
-    /// <param name="metadata">The dictionary containing the metadata.</param>
-    public FlagMetadata(Dictionary<string, object> metadata) : base(metadata)
-    {
-    }
-}
diff --git a/src/OpenFeature/Model/BaseMetadata.cs b/src/OpenFeature/Model/ImmutableMetadata.cs
similarity index 67%
rename from src/OpenFeature/Model/BaseMetadata.cs
rename to src/OpenFeature/Model/ImmutableMetadata.cs
index 876247df..40d452d0 100644
--- a/src/OpenFeature/Model/BaseMetadata.cs
+++ b/src/OpenFeature/Model/ImmutableMetadata.cs
@@ -1,16 +1,31 @@
 using System.Collections.Generic;
 using System.Collections.Immutable;
 
+#nullable enable
 namespace OpenFeature.Model;
 
 /// <summary>
-/// Represents the base class for metadata objects.
+/// Represents immutable metadata associated with feature flags and events.
 /// </summary>
-public abstract class BaseMetadata
+/// <seealso href="https://github.com/open-feature/spec/blob/v0.7.0/specification/types.md#flag-metadata"/>
+/// <seealso href="https://github.com/open-feature/spec/blob/v0.7.0/specification/types.md#event-metadata"/>
+public sealed class ImmutableMetadata
 {
     private readonly ImmutableDictionary<string, object> _metadata;
 
-    internal BaseMetadata(Dictionary<string, object> metadata)
+    /// <summary>
+    /// Constructor for the <see cref="ImmutableMetadata"/> class.
+    /// </summary>
+    public ImmutableMetadata()
+    {
+        this._metadata = ImmutableDictionary<string, object>.Empty;
+    }
+
+    /// <summary>
+    /// Constructor for the <see cref="ImmutableMetadata"/> class.
+    /// </summary>
+    /// <param name="metadata">The dictionary containing the metadata.</param>
+    public ImmutableMetadata(Dictionary<string, object> metadata)
     {
         this._metadata = metadata.ToImmutableDictionary();
     }
@@ -20,7 +35,7 @@ internal BaseMetadata(Dictionary<string, object> metadata)
     /// </summary>
     /// <param name="key">The key of the value to retrieve.</param>
     /// <returns>The boolean value associated with the key, or null if the key is not found.</returns>
-    public virtual bool? GetBool(string key)
+    public bool? GetBool(string key)
     {
         return this.GetValue<bool>(key);
     }
@@ -30,7 +45,7 @@ internal BaseMetadata(Dictionary<string, object> metadata)
     /// </summary>
     /// <param name="key">The key of the value to retrieve.</param>
     /// <returns>The integer value associated with the key, or null if the key is not found.</returns>
-    public virtual int? GetInt(string key)
+    public int? GetInt(string key)
     {
         return this.GetValue<int>(key);
     }
@@ -40,7 +55,7 @@ internal BaseMetadata(Dictionary<string, object> metadata)
     /// </summary>
     /// <param name="key">The key of the value to retrieve.</param>
     /// <returns>The double value associated with the key, or null if the key is not found.</returns>
-    public virtual double? GetDouble(string key)
+    public double? GetDouble(string key)
     {
         return this.GetValue<double>(key);
     }
@@ -50,7 +65,7 @@ internal BaseMetadata(Dictionary<string, object> metadata)
     /// </summary>
     /// <param name="key">The key of the value to retrieve.</param>
     /// <returns>The string value associated with the key, or null if the key is not found.</returns>
-    public virtual string? GetString(string key)
+    public string? GetString(string key)
     {
         var hasValue = this._metadata.TryGetValue(key, out var value);
         if (!hasValue)
diff --git a/src/OpenFeature/Model/ProviderEvents.cs b/src/OpenFeature/Model/ProviderEvents.cs
index 6feccfb0..fa22f7cd 100644
--- a/src/OpenFeature/Model/ProviderEvents.cs
+++ b/src/OpenFeature/Model/ProviderEvents.cs
@@ -3,40 +3,39 @@
 
 namespace OpenFeature.Model
 {
-    /// <summary>
-    /// The EventHandlerDelegate is an implementation of an Event Handler
-    /// </summary>
-    public delegate void EventHandlerDelegate(ProviderEventPayload? eventDetails);
-
-    /// <summary>
-    /// Contains the payload of an OpenFeature Event.
-    /// </summary>
-    public class ProviderEventPayload
-    {
         /// <summary>
-        /// Name of the provider.
+        /// The EventHandlerDelegate is an implementation of an Event Handler
         /// </summary>
-        public string? ProviderName { get; set; }
+        public delegate void EventHandlerDelegate(ProviderEventPayload? eventDetails);
 
         /// <summary>
-        /// Type of the event
+        /// Contains the payload of an OpenFeature Event.
         /// </summary>
-        public ProviderEventTypes Type { get; set; }
+        public class ProviderEventPayload
+        {
+                /// <summary>
+                /// Name of the provider.
+                /// </summary>
+                public string? ProviderName { get; set; }
 
-        /// <summary>
-        /// A message providing more information about the event.
-        /// </summary>
-        public string? Message { get; set; }
+                /// <summary>
+                /// Type of the event
+                /// </summary>
+                public ProviderEventTypes Type { get; set; }
 
-        /// <summary>
-        /// A List of flags that have been changed.
-        /// </summary>
-        public List<string>? FlagsChanged { get; set; }
+                /// <summary>
+                /// A message providing more information about the event.
+                /// </summary>
+                public string? Message { get; set; }
 
-        /// <summary>
-        /// Metadata information for the event.
-        /// </summary>
-        // TODO: This needs to be changed to a EventMetadata object
-        public Dictionary<string, object>? EventMetadata { get; set; }
-    }
+                /// <summary>
+                /// A List of flags that have been changed.
+                /// </summary>
+                public List<string>? FlagsChanged { get; set; }
+
+                /// <summary>
+                /// Metadata information for the event.
+                /// </summary>
+                public ImmutableMetadata? EventMetadata { get; set; }
+        }
 }
diff --git a/src/OpenFeature/Model/ResolutionDetails.cs b/src/OpenFeature/Model/ResolutionDetails.cs
index 5f686d47..4dda0e21 100644
--- a/src/OpenFeature/Model/ResolutionDetails.cs
+++ b/src/OpenFeature/Model/ResolutionDetails.cs
@@ -2,73 +2,73 @@
 
 namespace OpenFeature.Model
 {
-    /// <summary>
-    /// Defines the contract that the <see cref="FeatureProvider"/> is required to return
-    /// Describes the details of the feature flag being evaluated
-    /// </summary>
-    /// <typeparam name="T">Flag value type</typeparam>
-    /// <seealso href="https://github.com/open-feature/spec/blob/v0.7.0/specification/types.md#resolution-details"/>
-    public sealed class ResolutionDetails<T>
-    {
         /// <summary>
-        /// Feature flag evaluated value
+        /// Defines the contract that the <see cref="FeatureProvider"/> is required to return
+        /// Describes the details of the feature flag being evaluated
         /// </summary>
-        public T Value { get; }
+        /// <typeparam name="T">Flag value type</typeparam>
+        /// <seealso href="https://github.com/open-feature/spec/blob/v0.7.0/specification/types.md#resolution-details"/>
+        public sealed class ResolutionDetails<T>
+        {
+                /// <summary>
+                /// Feature flag evaluated value
+                /// </summary>
+                public T Value { get; }
 
-        /// <summary>
-        /// Feature flag key
-        /// </summary>
-        public string FlagKey { get; }
+                /// <summary>
+                /// Feature flag key
+                /// </summary>
+                public string FlagKey { get; }
 
-        /// <summary>
-        /// Error that occurred during evaluation
-        /// <see cref="ErrorType"/>
-        /// </summary>
-        public ErrorType ErrorType { get; }
+                /// <summary>
+                /// Error that occurred during evaluation
+                /// <see cref="ErrorType"/>
+                /// </summary>
+                public ErrorType ErrorType { get; }
 
-        /// <summary>
-        /// Message containing additional details about an error.
-        /// </summary>
-        public string? ErrorMessage { get; }
+                /// <summary>
+                /// Message containing additional details about an error.
+                /// </summary>
+                public string? ErrorMessage { get; }
 
-        /// <summary>
-        /// Describes the reason for the outcome of the evaluation process
-        /// <see cref="Reason"/>
-        /// </summary>
-        public string? Reason { get; }
+                /// <summary>
+                /// Describes the reason for the outcome of the evaluation process
+                /// <see cref="Reason"/>
+                /// </summary>
+                public string? Reason { get; }
 
-        /// <summary>
-        /// A variant is a semantic identifier for a value. This allows for referral to particular values without
-        /// necessarily including the value itself, which may be quite prohibitively large or otherwise unsuitable
-        /// in some cases.
-        /// </summary>
-        public string? Variant { get; }
+                /// <summary>
+                /// A variant is a semantic identifier for a value. This allows for referral to particular values without
+                /// necessarily including the value itself, which may be quite prohibitively large or otherwise unsuitable
+                /// in some cases.
+                /// </summary>
+                public string? Variant { get; }
 
-        /// <summary>
-        /// A structure which supports definition of arbitrary properties, with keys of type string, and values of type boolean, string, or number.
-        /// </summary>
-        public FlagMetadata? FlagMetadata { get; }
+                /// <summary>
+                /// A structure which supports definition of arbitrary properties, with keys of type string, and values of type boolean, string, or number.
+                /// </summary>
+                public ImmutableMetadata? FlagMetadata { get; }
 
-        /// <summary>
-        /// Initializes a new instance of the <see cref="ResolutionDetails{T}"/> class.
-        /// </summary>
-        /// <param name="flagKey">Feature flag key</param>
-        /// <param name="value">Evaluated value</param>
-        /// <param name="errorType">Error</param>
-        /// <param name="reason">Reason</param>
-        /// <param name="variant">Variant</param>
-        /// <param name="errorMessage">Error message</param>
-        /// <param name="flagMetadata">Flag metadata</param>
-        public ResolutionDetails(string flagKey, T value, ErrorType errorType = ErrorType.None, string? reason = null,
-            string? variant = null, string? errorMessage = null, FlagMetadata? flagMetadata = null)
-        {
-            this.Value = value;
-            this.FlagKey = flagKey;
-            this.ErrorType = errorType;
-            this.Reason = reason;
-            this.Variant = variant;
-            this.ErrorMessage = errorMessage;
-            this.FlagMetadata = flagMetadata;
+                /// <summary>
+                /// Initializes a new instance of the <see cref="ResolutionDetails{T}"/> class.
+                /// </summary>
+                /// <param name="flagKey">Feature flag key</param>
+                /// <param name="value">Evaluated value</param>
+                /// <param name="errorType">Error</param>
+                /// <param name="reason">Reason</param>
+                /// <param name="variant">Variant</param>
+                /// <param name="errorMessage">Error message</param>
+                /// <param name="flagMetadata">Flag metadata</param>
+                public ResolutionDetails(string flagKey, T value, ErrorType errorType = ErrorType.None, string? reason = null,
+                    string? variant = null, string? errorMessage = null, ImmutableMetadata? flagMetadata = null)
+                {
+                        this.Value = value;
+                        this.FlagKey = flagKey;
+                        this.ErrorType = errorType;
+                        this.Reason = reason;
+                        this.Variant = variant;
+                        this.ErrorMessage = errorMessage;
+                        this.FlagMetadata = flagMetadata;
+                }
         }
-    }
 }
diff --git a/test/OpenFeature.Tests/FlagMetadataTest.cs b/test/OpenFeature.Tests/ImmutableMetadataTest.cs
similarity index 91%
rename from test/OpenFeature.Tests/FlagMetadataTest.cs
rename to test/OpenFeature.Tests/ImmutableMetadataTest.cs
index d716d91e..344392b0 100644
--- a/test/OpenFeature.Tests/FlagMetadataTest.cs
+++ b/test/OpenFeature.Tests/ImmutableMetadataTest.cs
@@ -5,7 +5,7 @@
 
 namespace OpenFeature.Tests;
 
-public class FlagMetadataTest
+public class ImmutableMetadataTest
 {
     [Fact]
     [Specification("1.4.14",
@@ -13,7 +13,7 @@ public class FlagMetadataTest
     public void GetBool_Should_Return_Null_If_Key_Not_Found()
     {
         // Arrange
-        var flagMetadata = new FlagMetadata();
+        var flagMetadata = new ImmutableMetadata();
 
         // Act
         var result = flagMetadata.GetBool("nonexistentKey");
@@ -35,7 +35,7 @@ public void GetBool_Should_Return_Value_If_Key_Found()
                 "boolKey", true
             }
         };
-        var flagMetadata = new FlagMetadata(metadata);
+        var flagMetadata = new ImmutableMetadata(metadata);
 
         // Act
         var result = flagMetadata.GetBool("boolKey");
@@ -56,7 +56,7 @@ public void GetBool_Should_Throw_Value_Is_Invalid()
                 "wrongKey", "11a"
             }
         };
-        var flagMetadata = new FlagMetadata(metadata);
+        var flagMetadata = new ImmutableMetadata(metadata);
 
         // Act
         var result = flagMetadata.GetBool("wrongKey");
@@ -71,7 +71,7 @@ public void GetBool_Should_Throw_Value_Is_Invalid()
     public void GetInt_Should_Return_Null_If_Key_Not_Found()
     {
         // Arrange
-        var flagMetadata = new FlagMetadata();
+        var flagMetadata = new ImmutableMetadata();
 
         // Act
         var result = flagMetadata.GetInt("nonexistentKey");
@@ -93,7 +93,7 @@ public void GetInt_Should_Return_Value_If_Key_Found()
                 "intKey", 1
             }
         };
-        var flagMetadata = new FlagMetadata(metadata);
+        var flagMetadata = new ImmutableMetadata(metadata);
 
         // Act
         var result = flagMetadata.GetInt("intKey");
@@ -115,7 +115,7 @@ public void GetInt_Should_Throw_Value_Is_Invalid()
                 "wrongKey", "11a"
             }
         };
-        var flagMetadata = new FlagMetadata(metadata);
+        var flagMetadata = new ImmutableMetadata(metadata);
 
         // Act
         var result = flagMetadata.GetInt("wrongKey");
@@ -130,7 +130,7 @@ public void GetInt_Should_Throw_Value_Is_Invalid()
     public void GetDouble_Should_Return_Null_If_Key_Not_Found()
     {
         // Arrange
-        var flagMetadata = new FlagMetadata();
+        var flagMetadata = new ImmutableMetadata();
 
         // Act
         var result = flagMetadata.GetDouble("nonexistentKey");
@@ -152,7 +152,7 @@ public void GetDouble_Should_Return_Value_If_Key_Found()
                 "doubleKey", 1.2
             }
         };
-        var flagMetadata = new FlagMetadata(metadata);
+        var flagMetadata = new ImmutableMetadata(metadata);
 
         // Act
         var result = flagMetadata.GetDouble("doubleKey");
@@ -174,7 +174,7 @@ public void GetDouble_Should_Throw_Value_Is_Invalid()
                 "wrongKey", "11a"
             }
         };
-        var flagMetadata = new FlagMetadata(metadata);
+        var flagMetadata = new ImmutableMetadata(metadata);
 
         // Act
         var result = flagMetadata.GetDouble("wrongKey");
@@ -189,7 +189,7 @@ public void GetDouble_Should_Throw_Value_Is_Invalid()
     public void GetString_Should_Return_Null_If_Key_Not_Found()
     {
         // Arrange
-        var flagMetadata = new FlagMetadata();
+        var flagMetadata = new ImmutableMetadata();
 
         // Act
         var result = flagMetadata.GetString("nonexistentKey");
@@ -211,7 +211,7 @@ public void GetString_Should_Return_Value_If_Key_Found()
                 "stringKey", "11"
             }
         };
-        var flagMetadata = new FlagMetadata(metadata);
+        var flagMetadata = new ImmutableMetadata(metadata);
 
         // Act
         var result = flagMetadata.GetString("stringKey");
@@ -233,7 +233,7 @@ public void GetString_Should_Throw_Value_Is_Invalid()
                 "wrongKey", new object()
             }
         };
-        var flagMetadata = new FlagMetadata(metadata);
+        var flagMetadata = new ImmutableMetadata(metadata);
 
         // Act
         var result = flagMetadata.GetString("wrongKey");
diff --git a/test/OpenFeature.Tests/OpenFeatureEventTests.cs b/test/OpenFeature.Tests/OpenFeatureEventTests.cs
index 599cea30..3a373c98 100644
--- a/test/OpenFeature.Tests/OpenFeatureEventTests.cs
+++ b/test/OpenFeature.Tests/OpenFeatureEventTests.cs
@@ -25,12 +25,7 @@ public async Task Event_Executor_Should_Propagate_Events_ToGlobal_Handler()
 
             eventExecutor.AddApiLevelHandler(ProviderEventTypes.ProviderConfigurationChanged, eventHandler);
 
-            var eventMetadata = new Dictionary<string, object>
-            {
-                {
-                    "foo", "bar"
-                }
-            };
+            var eventMetadata = new ImmutableMetadata(new Dictionary<string, object> { { "foo", "bar" } });
             var myEvent = new Event
             {
                 EventPayload = new ProviderEventPayload