With the release of Windows Phone 7, Metro UI become very much popular and then Microsoft continue to use this UI in its upcoming Windows 8.
Many applications are now coming with Metro UI design and icons, if you are too looking for some nice and cool Metro icons then here is a Free Metro UI Icon pack for Windows, it is a set of beautifully designed application icons, which is in line with all of the requirements of the WP7 and Windows 8 operating systems.
All the icons are 48×48 pixels in size. The actual image is located in a central square of 26×26 pixels, and the borders are transparent.