Windows 8 Metro apps do not have a traditional close (X)
button.
There are two common ways to close an app
1. ALT + F4
Press keys ALT + F4 and it will close the current active app.
2. Use Close gesture
To close an app in Windows 8, first we need to view all opened apps.
Move your mouse to the top-left corner in the metro view of Windows 8.
You will see a list of all opened apps.
Right click on the app you want to close and select the Close menu. This will close the app.