diff --git a/README.md b/README.md
index cfbcbac..e55bedf 100644
--- a/README.md
+++ b/README.md
@@ -11,7 +11,7 @@ A Metalsmith plugin to render markdown files to HTML, using [Marked](https://git
 ## Features
 
 - Compiles `.md` and `.markdown` files in `metalsmith.source()` to HTML.
-- Enables rendering file metadata keys to HTML through the [keys option](#rendering-file-metadata)
+- Enables rendering file or metalsmith metadata keys to HTML through the [keys option](#rendering-metadata)
 - Define a dictionary of markdown globalRefs (for links, images) available to all render targets
 - Supports using the markdown library of your choice through the [render option](#using-another-markdown-library)
 
@@ -75,17 +75,28 @@ metalsmith.use(
 - `render` - Specify a custom render function with the signature `(source, engineOptions, context) => string`. `context` is an object with the signature `{ path:string, key:string }` where the `path` key contains the current file path, and `key` contains the target metadata key.
 - `engineOptions` Options to pass to the markdown engine (default [marked](https://github.com/markedjs/marked))
 
-### Rendering file metadata
+### Rendering metadata
 
-You can render markdown to HTML in file metadata keys by specifying the `keys` option.  
-The `keys` option also supports dot-delimited key-paths.
+You can render markdown to HTML in file or metalsmith metadata keys by specifying the `keys` option.  
+The `keys` option also supports dot-delimited key-paths. You can also use [globalRefs within them](#defining-a-dictionary-of-markdown-globalrefs)
 
 ```js
-metalsmith.use(
-  markdown({
-    keys: ['html_desc', 'nested.data']
+metalsmith
+  .metadata({
+    from_metalsmith_metadata: 'I _shall_ become **markdown** and can even use a [globalref][globalref_link]',
+    markdownRefs: {
+      globalref_link: 'https://johndoe.com'
+    }
   })
-)
+  .use(
+    markdown({
+      keys: {
+        files: ['html_desc', 'nested.data'],
+        global: ['from_metalsmith_metadata']
+      },
+      globalRefs: 'markdownRefs'
+    })
+  )
 ```
 
 You can even render all keys at a certain path by setting the `wildcard` option and using a globstar `*` in the keypaths.  
@@ -170,7 +181,7 @@ metalsith
   // eg in a markdown file: [My Twitter profile][twitter]
   .use(markdown({ globalRefs: 'global.links' }))
   // eg in a handlebars layout: {{ global.links.twitter }}
-  .use(layouts())
+  .use(layouts({ pattern: '**/*.html' }))
 ```
 
 ### Custom markdown rendering
diff --git a/lib/index.d.ts b/lib/index.d.ts
index 1f7057c..fd2422e 100644
--- a/lib/index.d.ts
+++ b/lib/index.d.ts
@@ -10,11 +10,15 @@ export type Render<E> = (source: string, engineOptions: EngineOptions<E>, contex
 
 export type Options<E = marked.MarkedOptions> = {
     /**
-     * - Key names of file metadata to render to HTML - can be nested
+     * - Array of file metadata key names or object with arrays of key names of file or global metadata key names to render to HTML - can be nested keypaths
      */
-    keys?: string[];
+    keys?: string[] | {
+      files: string[]
+      global: string[]
+    };
     /**
      * - Expand `*` wildcards in keypaths
+     * @default false
      */
     wildcard?: boolean;
     /**
diff --git a/src/index.js b/src/index.js
index 9ef4d0e..82dc5cb 100644
--- a/src/index.js
+++ b/src/index.js
@@ -23,7 +23,7 @@ function refsObjectToMarkdown(refsObject) {
 
 /**
  * @typedef Options
- * @property {string[]} [keys] - Key names of file metadata to render to HTML - can be nested
+ * @property {string[]|{files: string[], global: string[]}} [keys] - Key names of file metadata to render to HTML - can be nested
  * @property {boolean} [wildcard=false] - Expand `*` wildcards in keypaths
  * @property {string|Object<string, string>} [globalRefs] An object of `{ refname: 'link' }` pairs that will be made available for all markdown files and keys,
  * or a `metalsmith.metadata()` keypath containing such object
@@ -33,7 +33,7 @@ function refsObjectToMarkdown(refsObject) {
  **/
 
 const defaultOptions = {
-  keys: [],
+  keys: {},
   wildcard: false,
   render: defaultRender,
   engineOptions: {},
@@ -52,10 +52,31 @@ function markdown(options = defaultOptions) {
     options = Object.assign({}, defaultOptions, options)
   }
 
+  if (Array.isArray(options.keys)) {
+    options.keys = { files: options.keys }
+  }
+
   return function markdown(files, metalsmith, done) {
     const debug = metalsmith.debug('@metalsmith/markdown')
     const matches = metalsmith.match('**/*.{md,markdown}', Object.keys(files))
 
+    function renderKeys(keys, prepend, target, path) {
+      if (options.wildcard) {
+        keys = expandWildcardKeypaths(target, keys, '*')
+      }
+
+      keys.forEach((key) => {
+        const value = get(target, key)
+        if (typeof value === 'string') {
+          const context = path === 'metalsmith.metadata()' ? { key } : { path, key }
+          debug.info('Rendering key "%s" of target "%s"', key.join ? key.join('.') : key, path)
+          set(target, key, options.render(prepend + value, options.engineOptions, context))
+        } else if (typeof value !== 'undefined') {
+          debug.warn('Couldn\'t render key "%s" of target "%s": not a string', key.join ? key.join('.') : key, path)
+        }
+      })
+    }
+
     const legacyEngineOptions = Object.keys(options).filter((opt) => !Object.keys(defaultOptions).includes(opt))
     if (legacyEngineOptions.length) {
       debug.warn('Starting from version 2.0 marked engine options will need to be specified as options.engineOptions')
@@ -101,25 +122,19 @@ function markdown(options = defaultOptions) {
       })
       data.contents = Buffer.from(str)
 
-      let keys = options.keys
-      if (options.wildcard) {
-        keys = expandWildcardKeypaths(data, options.keys, '*')
-      }
-      keys.forEach((key) => {
-        const value = get(data, key)
-        if (typeof value === 'string') {
-          debug.info('Rendering key "%s" of file "%s"', key.join ? key.join('.') : key, file)
-          set(data, key, options.render(globalRefsMarkdown + value, options.engineOptions, { path: file, key }))
-          // log a warning if the key is defined and of an unexpected type, but not if the property simply is not defined
-        } else if (typeof value !== 'undefined') {
-          debug.warn('Couldn\'t render key "%s" of file "%s": not a string', key.join ? key.join('.') : key, file)
-        }
-      })
+      const keys = options.keys && options.keys.files ? options.keys.files : []
+      renderKeys(keys, globalRefsMarkdown, data, file)
 
       delete files[file]
       files[html] = data
     })
 
+    if (options.keys && options.keys.global) {
+      debug.info('Processing metalsmith.metadata()')
+      const meta = metalsmith.metadata()
+      renderKeys(options.keys.global, globalRefsMarkdown, meta, 'metalsmith.metadata()')
+    }
+
     done()
   }
 }
diff --git a/test/index.js b/test/index.js
index 31c0289..b50a58b 100644
--- a/test/index.js
+++ b/test/index.js
@@ -272,7 +272,7 @@ describe('@metalsmith/markdown', function () {
         if (err) done(err)
         try {
           assert.deepStrictEqual(output.slice(0, 1), [
-            ['warn', 'Couldn\'t render key "%s" of file "%s": not a string', 'not_a_string', 'index.md']
+            ['warn', 'Couldn\'t render key "%s" of target "%s": not a string', 'not_a_string', 'index.md']
           ])
           done()
         } catch (err) {
@@ -326,6 +326,37 @@ describe('@metalsmith/markdown', function () {
       })
   })
 
+  it('should render keys in metalsmith.metadata()', function (done) {
+    const ms = msCommon('test/fixtures/basic')
+    ms.env('DEBUG', '@metalsmith/mardown*')
+      .metadata({
+        markdownRefs: {
+          defined_link: 'https://globalref.io'
+        },
+        has_markdown: '**[globalref_link][defined_link]**'
+      })
+      .use(
+        markdown({
+          keys: {
+            global: ['has_markdown']
+          },
+          globalRefs: 'markdownRefs'
+        })
+      )
+      .process((err) => {
+        if (err) done(err)
+        try {
+          assert.strictEqual(
+            ms.metadata().has_markdown,
+            '<p><strong><a href="https://globalref.io">globalref_link</a></strong></p>\n'
+          )
+          done()
+        } catch (err) {
+          done(err)
+        }
+      })
+  })
+
   it('expandWildCardKeyPath should throw if root is not an object', function () {
     try {
       expandWildcardKeypath(null, [], '*')