C:\Users\{user name}\AppData\Local\Microsoft\Windows\Application Shortcuts folder and the
C:\ProgramData\Microsoft\Windows\Start Menu\Programs folder

are the two folders that contain all the information for the Metro interface. All of the apps that appear on it are here. Before messing about with the Metro icons, backup these two folders so that you can easily recover any goofs by just copy and paste.

Ask me how I know about these "goofs", heh.