I got asked this today, Windows 8 metro apps don’t have a close button so how do you quit them. Well there are a number of ways. The most common way is, don’t, let the OS do it when it needs more memory for something it will close ones you already have open. This way the most likely apps you will be using will be ready for you already open unless the memory is needed.
The second way is using your finger/mouse flick/drag the app down to the bottom of the screen. It will close when you push it off the bottom of the screen and let go. The third is to use the Alt+F4 key combo that has been around since the first days of Windows. Fourth use task manager to check what apps are running and close the ones you don’t want running. You might only want to do this if you are sure of what you are doing.
To close Windows itself (not Windows RT) on the desktop press the Alt-F4 keys and the old style Windows shutdown dialog is presented.