Microsoft’s Metro design principles are rapidly becoming an industry standard on touch-enabled devices, including PCs, tablets, and smartphones phones. The technology is incredibly powerful, even for small screens. The intuitive UI topography and large fonts are replacing complicated menus and extensive descriptions.

Here are the five most powerful Metro concepts:
1. Live Tiles instead of icons and lists. Represent a list of objects as a set of rectangles. Identify the object by name or a simple picture and put the most important news on the tile.

2. Panorama view instead of menus. Place multiple views side-to-side one after another. A small piece of the next page will invite the user to slide right. Grayed titles of the next views help to navigate.

3. Semantic Zoom and Infinite Canvas instead of complex grids. Eliminate the perception of complexity, showing more details as the user zooms in and fewer details as the user zooms out.

4. Search instead of nested folders. As a user searches in any list and across applications, there is no need to maintain nested folder structures.

5. Pinned Tiles, Cross-App Sharing and Shopping Carts bring notion of Favorites to the next level. A user can pick a tile deeply inside an application and place it to the home screen, shopping cart or another application, enabling quick access in a relevant place.

References:

http://msdn.microsoft.com/en-us/library/windows/apps/hh465319.aspx
Microsoft Tech Days: Metro UI/ Interaction Design Guidelines
http://en.wikipedia.org/wiki/Metro_(design_language)
http://msdn.microsoft.com/en-us/library/windows/apps/hh465233.aspx