diff --git a/lib/index.js b/lib/index.js
index 45793f1..8e62b62 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -1,4 +1,3 @@
-
 var debug = require('debug')('metalsmith-collections');
 var extend = require('extend');
 var multimatch = require('multimatch');
@@ -20,26 +19,25 @@ module.exports = plugin;
  * @return {Function}
  */
 
-function plugin(opts, globalOpts){
+function plugin(opts, globalOpts) {
   opts = normalize(opts);
   var keys = Object.keys(opts);
   var match = matcher(opts);
 
-  return function(files, metalsmith, done){
+  return function(files, metalsmith, done) {
     var metadata = metalsmith.metadata();
 
     /**
      * Find the files in each collection.
      */
 
-    Object.keys(files).forEach(function(file){
+    Object.keys(files).forEach(function(file) {
       debug('checking file: %s', file);
       var data = files[file];
+      data.path = file;
 
-      data.path = file
-
-      match(file, data).forEach(function(key){
-        if (key && keys.indexOf(key) < 0){
+      Object.keys(match(file, data)).forEach(function(key) {
+        if (key && keys.indexOf(key) < 0) {
           opts[key] = {};
           keys.push(key);
         }
@@ -53,7 +51,7 @@ function plugin(opts, globalOpts){
      * Ensure that a default empty collection exists.
      */
 
-    keys.forEach(function(key) {
+    Object.keys(keys).forEach(function(key) {
       metadata[key] = metadata[key] || [];
     });
 
@@ -61,8 +59,8 @@ function plugin(opts, globalOpts){
      * Merge global options with collection options
      */
 
-    keys.forEach(function(key){
-      for(var gKey in globalOpts){
+    keys.forEach(function(key) {
+      for (var gKey in globalOpts) {
         opts[key][gKey] = opts[key][gKey] || globalOpts[gKey];
       }
     });
@@ -70,19 +68,18 @@ function plugin(opts, globalOpts){
     /**
      * Sort the collections.
      */
-
-    keys.forEach(function(key){
+    keys.forEach(function(key) {
       debug('sorting collection: %s', key);
       var settings = opts[key];
-      var sort = settings.sortBy || (globalOpts.sortBy || 'date');
+      var sort = settings.sortBy || 'date';
       var col = metadata[key];
 
       if ('function' == typeof sort) {
         col.sort(sort);
       } else {
-        col.sort(function(a, b){
-          a = a[sort];
-          b = b[sort];
+        col.sort(function(a, b) {
+          a = (a.collection[key]) ? (a.collection[key][sort] || a[sort]) : a[sort];
+          b = (b.collection[key]) ? (b.collection[key][sort] || b[sort]) : b[sort];
           if (!a && !b) return 0;
           if (!a) return -1;
           if (!b) return 1;
@@ -99,19 +96,19 @@ function plugin(opts, globalOpts){
      * Add `next` and `previous` references and apply the `limit` option
      */
 
-    keys.forEach(function(key){
+    keys.forEach(function(key) {
       debug('referencing collection: %s', key);
       var settings = opts[key];
       var col = metadata[key];
       var last = col.length - 1;
       if (opts[key].limit && opts[key].limit < col.length) {
-          col = metadata[key] = col.slice(0, opts[key].limit);
-          last = opts[key].limit - 1;
+        col = metadata[key] = col.slice(0, opts[key].limit);
+        last = opts[key].limit - 1;
       }
       if (settings.refer === false) return;
-      col.forEach(function(file, i){
-        if (0 != i) file.previous = col[i-1];
-        if (last != i) file.next = col[i+1];
+      col.forEach(function(file, i) {
+        if (0 != i) file.previous = col[i - 1];
+        if (last != i) file.next = col[i + 1];
       });
     });
 
@@ -119,13 +116,15 @@ function plugin(opts, globalOpts){
      * Add collection metadata
      */
 
-    keys.forEach(function(key){
+    keys.forEach(function(key) {
       debug('adding metadata: %s', key);
       var settings = opts[key];
       var col = metadata[key];
       col.metadata = (typeof settings.metadata === 'string') ?
         loadMetadata(settings.metadata) :
-        settings.metadata;
+        (settings.metadata || {});
+
+      Object.assign(col.metadata, globalOpts);
     });
 
     /**
@@ -133,7 +132,7 @@ function plugin(opts, globalOpts){
      */
 
     metadata.collections = {};
-    keys.forEach(function(key){
+    keys.forEach(function(key) {
       return metadata.collections[key] = metadata[key];
     });
 
@@ -147,13 +146,17 @@ function plugin(opts, globalOpts){
  * @param {Object} options
  */
 
-function normalize(options){
+function normalize(options) {
   options = options || {};
 
   for (var key in options) {
     var val = options[key];
-    if ('string' == typeof val) options[key] = { pattern: val };
-    if (val instanceof Array) options[key] = { pattern: val };
+    if ('string' == typeof val) options[key] = {
+      pattern: val
+    };
+    if (val instanceof Array) options[key] = {
+      pattern: val
+    };
   }
 
   return options;
@@ -166,31 +169,44 @@ function normalize(options){
  * @return {Function}
  */
 
-function matcher(cols){
+function matcher(cols) {
   var keys = Object.keys(cols);
   var matchers = {};
 
-  keys.forEach(function(key){
+  keys.forEach(function(key) {
     var opts = cols[key];
     if (!opts.pattern) {
       return;
     }
     matchers[key] = {
       match: function(file) {
-        return multimatch(file, opts.pattern)
+        return multimatch(file, opts.pattern);
       }
     };
   });
 
-  return function(file, data){
+  return function(file, data) {
     var matches = [];
 
     if (data.collection) {
       var collection = data.collection;
-      if (!Array.isArray(collection)) {
-        collection = [collection];
+      let tmpCollection = {};
+
+      if (Array.isArray(collection)) {
+        for (let collItem of collection) {
+          tmpCollection[collItem] = {};
+        }
+      } else if (collection.constructor === String)
+        tmpCollection[collection] = {};
+      else if (collection instanceof Object)
+        tmpCollection = collection;
+      else {
+        collection = {};
       }
-      collection.forEach(function(key){
+
+      collection = data.collection = tmpCollection;
+
+      Object.keys(collection).forEach(function(key) {
         matches.push(key);
 
         if (key && keys.indexOf(key) < 0) {
@@ -199,14 +215,13 @@ function matcher(cols){
       });
     }
 
-    for (var key in matchers){
+    for (var key in matchers) {
       var m = matchers[key];
       if (m.match(file).length) {
         matches.push(key);
       }
     }
 
-    data.collection = unique(matches);
-    return data.collection;
+    return data.collection || {};
   };
 }