diff --git a/client.go b/client.go
index 804024e49..ef130be1d 100644
--- a/client.go
+++ b/client.go
@@ -112,7 +112,7 @@ func (c *Client) Call(ctx context.Context, service, method string, req, resp int
 	)
 
 	if metadata, ok := GetMetadata(ctx); ok {
-		creq.Metadata = metadata
+		metadata.setRequest(creq)
 	}
 
 	if dl, ok := ctx.Deadline(); ok {
diff --git a/example/cmd/main.go b/example/cmd/main.go
index f452381ee..f1f43ab70 100644
--- a/example/cmd/main.go
+++ b/example/cmd/main.go
@@ -109,7 +109,7 @@ func client() error {
 	}
 
 	ctx := context.Background()
-	md := ttrpc.Metadata{}
+	md := ttrpc.MD{}
 	md.Set("name", "koye")
 	ctx = ttrpc.WithMetadata(ctx, md)
 
diff --git a/metadata.go b/metadata.go
index d03626321..ce8c0d13c 100644
--- a/metadata.go
+++ b/metadata.go
@@ -16,53 +16,74 @@
 
 package ttrpc
 
-import "context"
+import (
+	"context"
+	"strings"
+)
 
-// Metadata represents the key-value pairs (similar to http.Header) to be passed to ttrpc server from a client.
-type Metadata map[string]StringList
+// MD is the user type for ttrpc metadata
+type MD map[string][]string
 
 // Get returns the metadata for a given key when they exist.
 // If there is no metadata, a nil slice and false are returned.
-func (m Metadata) Get(key string) ([]string, bool) {
+func (m MD) Get(key string) ([]string, bool) {
+	key = strings.ToLower(key)
 	list, ok := m[key]
-	if !ok || len(list.List) == 0 {
+	if !ok || len(list) == 0 {
 		return nil, false
 	}
 
-	return list.List, true
+	return list, true
 }
 
 // Set sets the provided values for a given key.
 // The values will overwrite any existing values.
 // If no values provided, a key will be deleted.
-func (m Metadata) Set(key string, values ...string) {
+func (m MD) Set(key string, values ...string) {
+	key = strings.ToLower(key)
 	if len(values) == 0 {
 		delete(m, key)
 		return
 	}
-
-	m[key] = StringList{List: values}
+	m[key] = values
 }
 
 // Append appends additional values to the given key.
-func (m Metadata) Append(key string, values ...string) {
+func (m MD) Append(key string, values ...string) {
+	key = strings.ToLower(key)
 	if len(values) == 0 {
 		return
 	}
-
-	list, ok := m[key]
+	current, ok := m[key]
 	if ok {
-		m.Set(key, append(list.List, values...)...)
+		m.Set(key, append(current, values...)...)
 	} else {
 		m.Set(key, values...)
 	}
 }
 
+func (m MD) setRequest(r *Request) {
+	for k, values := range m {
+		for _, v := range values {
+			r.Metadata = append(r.Metadata, &KeyValue{
+				Key:   k,
+				Value: v,
+			})
+		}
+	}
+}
+
+func (m MD) fromRequest(r *Request) {
+	for _, kv := range r.Metadata {
+		m[kv.Key] = append(m[kv.Key], kv.Value)
+	}
+}
+
 type metadataKey struct{}
 
 // GetMetadata retrieves metadata from context.Context (previously attached with WithMetadata)
-func GetMetadata(ctx context.Context) (Metadata, bool) {
-	metadata, ok := ctx.Value(metadataKey{}).(Metadata)
+func GetMetadata(ctx context.Context) (MD, bool) {
+	metadata, ok := ctx.Value(metadataKey{}).(MD)
 	return metadata, ok
 }
 
@@ -81,6 +102,6 @@ func GetMetadataValue(ctx context.Context, name string) (string, bool) {
 }
 
 // WithMetadata attaches metadata map to a context.Context
-func WithMetadata(ctx context.Context, headers Metadata) context.Context {
-	return context.WithValue(ctx, metadataKey{}, headers)
+func WithMetadata(ctx context.Context, md MD) context.Context {
+	return context.WithValue(ctx, metadataKey{}, md)
 }
diff --git a/metadata_test.go b/metadata_test.go
index c334e059e..d7fc09559 100644
--- a/metadata_test.go
+++ b/metadata_test.go
@@ -21,8 +21,8 @@ import (
 	"testing"
 )
 
-func TestMetadata_Get(t *testing.T) {
-	metadata := make(Metadata)
+func TestMetadataGet(t *testing.T) {
+	metadata := make(MD)
 	metadata.Set("foo", "1", "2")
 
 	if list, ok := metadata.Get("foo"); !ok {
@@ -36,8 +36,8 @@ func TestMetadata_Get(t *testing.T) {
 	}
 }
 
-func TestMetadata_GetInvalidKey(t *testing.T) {
-	metadata := make(Metadata)
+func TestMetadataGetInvalidKey(t *testing.T) {
+	metadata := make(MD)
 	metadata.Set("foo", "1", "2")
 
 	if _, ok := metadata.Get("invalid"); ok {
@@ -45,8 +45,8 @@ func TestMetadata_GetInvalidKey(t *testing.T) {
 	}
 }
 
-func TestMetadata_Unset(t *testing.T) {
-	metadata := make(Metadata)
+func TestMetadataUnset(t *testing.T) {
+	metadata := make(MD)
 	metadata.Set("foo", "1", "2")
 	metadata.Set("foo")
 
@@ -55,8 +55,8 @@ func TestMetadata_Unset(t *testing.T) {
 	}
 }
 
-func TestMetadata_Replace(t *testing.T) {
-	metadata := make(Metadata)
+func TestMetadataReplace(t *testing.T) {
+	metadata := make(MD)
 	metadata.Set("foo", "1", "2")
 	metadata.Set("foo", "3", "4")
 
@@ -71,8 +71,8 @@ func TestMetadata_Replace(t *testing.T) {
 	}
 }
 
-func TestMetadata_Append(t *testing.T) {
-	metadata := make(Metadata)
+func TestMetadataAppend(t *testing.T) {
+	metadata := make(MD)
 	metadata.Set("foo", "1")
 	metadata.Append("foo", "2")
 	metadata.Append("bar", "3")
@@ -94,8 +94,8 @@ func TestMetadata_Append(t *testing.T) {
 	}
 }
 
-func TestMetadata_Context(t *testing.T) {
-	metadata := make(Metadata)
+func TestMetadataContext(t *testing.T) {
+	metadata := make(MD)
 	metadata.Set("foo", "bar")
 
 	ctx := WithMetadata(context.Background(), metadata)
diff --git a/server.go b/server.go
index 5c33559f6..f5d87ba46 100644
--- a/server.go
+++ b/server.go
@@ -469,8 +469,10 @@ func (c *serverConn) run(sctx context.Context) {
 var noopFunc = func() {}
 
 func getRequestContext(ctx context.Context, req *Request) (retCtx context.Context, cancel func()) {
-	if req.Metadata != nil {
-		ctx = WithMetadata(ctx, req.Metadata)
+	if len(req.Metadata) > 0 {
+		md := MD{}
+		md.fromRequest(req)
+		ctx = WithMetadata(ctx, md)
 	}
 
 	cancel = noopFunc
diff --git a/server_test.go b/server_test.go
index d76ece1b8..2af8c4a70 100644
--- a/server_test.go
+++ b/server_test.go
@@ -546,7 +546,7 @@ func roundTrip(ctx context.Context, t *testing.T, client *testingClient, value s
 		}
 	)
 
-	ctx = WithMetadata(ctx, Metadata{"foo": makeStringList("bar")})
+	ctx = WithMetadata(ctx, MD{"foo": []string{"bar"}})
 
 	resp, err := client.Test(ctx, tp)
 	if err != nil {
diff --git a/types.go b/types.go
index c8ecb3868..9a1c19a72 100644
--- a/types.go
+++ b/types.go
@@ -23,11 +23,11 @@ import (
 )
 
 type Request struct {
-	Service     string   `protobuf:"bytes,1,opt,name=service,proto3"`
-	Method      string   `protobuf:"bytes,2,opt,name=method,proto3"`
-	Payload     []byte   `protobuf:"bytes,3,opt,name=payload,proto3"`
-	TimeoutNano int64    `protobuf:"varint,4,opt,name=timeout_nano,proto3"`
-	Metadata    Metadata `protobuf:"bytes,5,opt,name=metadata,proto3" protobuf_key:"bytes,1,opt,name=key,proto3" protobuf_val:"bytes,2,opt,name=value,proto3"`
+	Service     string      `protobuf:"bytes,1,opt,name=service,proto3"`
+	Method      string      `protobuf:"bytes,2,opt,name=method,proto3"`
+	Payload     []byte      `protobuf:"bytes,3,opt,name=payload,proto3"`
+	TimeoutNano int64       `protobuf:"varint,4,opt,name=timeout_nano,proto3"`
+	Metadata    []*KeyValue `protobuf:"bytes,5,rep,name=metadata,proto3"`
 }
 
 func (r *Request) Reset()         { *r = Request{} }
@@ -52,3 +52,12 @@ func (r *StringList) String() string { return fmt.Sprintf("%+#v", r) }
 func (r *StringList) ProtoMessage()  {}
 
 func makeStringList(item ...string) StringList { return StringList{List: item} }
+
+type KeyValue struct {
+	Key   string `protobuf:"bytes,1,opt,name=key,proto3"`
+	Value string `protobuf:"bytes,2,opt,name=value,proto3"`
+}
+
+func (m *KeyValue) Reset()         { *m = KeyValue{} }
+func (*KeyValue) ProtoMessage()    {}
+func (m *KeyValue) String() string { return fmt.Sprintf("%+#v", m) }