Syncfusion Metro Studio is a collection of over 2500 Metro-style icon templates that can be easily customized to create thousands of unique Metro icons. 2500 Metro Style Icons for free.

This is more than just a catalogue of icons, you can manipulate them or create custom icons packs and export them all using Metro Studio software that comes with these icons installed within it. Watch the video on their site and it will show you what you can do.

Can these icons be used in commercial applications?

Yes, the icons are available royalty-free and can be used in commercial applications. Icons can also be used in open source projects and hosted on sites including but not limited to CodePlex, GitHub, BitBucket etc.