At a glance there is no (x) button to close Windows 8 Metro app. Then how you going to close all the Apps which are not required? Microsoft implemented smart way to close the applications when it notice that a app is no longer in use. However, I personally think that I need a quick and easy way to close it when I do not require it. Following are the couple of ways that you can use to close Metro App in Windows 8.
Method 1: Task Manager is one way to close a running metro app. Press ctrl + shift + esc or go to Desktop, right click on the task bar, and click Task Manager to open Task Manager. Then select the application you need to close and click End Task to close the application.
However, this is the method most of Windows users use to close running programs when it stuck. So, you may hate this method.
Method 2: You can use ATL + f4 to close any metro application. I know you will love this method.
Method 3: Move mouse pointer to top left hand corner of the screen. It will show the lastly used app. Drag the mouse towards bottom left hand corner. It will show all the other applications opened and running on the background. Right click on any of the open application and click close.
I hope now you have enough ways to close a Metro App in Windows 8.