In previous windows when the Windows key was pressed the start menu used to pop up. In the similar manner in Windows 8 when this key is pressed then the Metro start Screen opens up.
Win + D:
To view the old windows desktop these both key should be pressed altogether.
Win + C:
In order to view the Charm menu, Win + C key are used. Later on you can change the settings, share or search any program of folder.
Win + I:
These keys will help in opening the setting panel. In the setting panel the settings for the current app, wireless network, volume, brightness and shutdown can be changed.
Win + Z
These two keys help in opening the bar for the current Metro application.
Win + H
To open the Metro Share Panel click these two keys altogether.
Win + Q:
The Metro App Search screen will appear when Win + Q are selected.
Win + W
The Metro Setting Search Screen is viewed with the help of these two keys.
Win + F
The metro File search screen is brought into view
Win + K
If you wish to connect to a projector or some other device then take help from Win and K keys.
Win + ,
For an Aero Peek at the desktop use win and , keys together
Win + .
The current Metro application is snapped to the right side of the screen.
Win + Shift + .
The current Metro application is snapped towards the left side of the screen.
Win + J
The focus between the snapped Metro applications is switched.
Win + Page up / Down
The current app is moved to the other monitor
Win + tab
The application switcher menu is opened and the applications are switched.