Every so often we cover tools that help out developers, but this is in another league. A company called SyncFusion has created a product called Metro Studio 1 which looks to be invaluable to developers and designers alike. The company traditionally develops .NET components for ASP.NET, WPF, WinForms, Silverlight, WP7 and others.
Metro Studio 1 comes with 600 unique metro icons that can then be customized through the interface. You can change the size, padding, background shape, and colors of any icon. Plus, the XAML source is provided for the icons, or you can save the PNG. Every icon is vector based (hence why the XAML source is available), so exporting at any size is possible.
Best of all, the studio is totally free, and every icon is royalty-free and can be used in commercial projects.
So go on, download it now. Thanks, @rmaclean