I’ve been playing around with Windows 8 Consumer Preview for a few days now and it’s definitely taking me a little time to get used to the whole change in the UI. Along with the Start button being removed, you now have to access the new Metro apps in an odd hovering way.
When you open a Metro app in Windows 8 and you go back to the desktop, let’s say, you’ll notice that the taskbar remains empty. The metro app that you opened is no visible in the taskbar like you would normally think. With every release of Windows, when you open a program, it appears in the taskbar. In Windows 8, this is true of most normal programs, but not so with the full-screen metro apps designed specifically for Windows 8.
Previously, I wrote about how to exit a Metro app because it was not very clear! That was a first release of Windows 8 and things have changed in the Consumer Preview. According to Microsoft, there were over 100,000 changes between the first preview release of Windows and the current one!
In the latest release, to exit a Metro app (but no close), you have to move your mouse to either the top left or bottom left of the screen. If you move to the top left, you’ll see the previous window you had open. This is kind of like the Back button in IE.

As you can see in the screenshot above, I’m in the Mail app, but if I move to the top left, I get a screenshot of the desktop, which was the last thing I had open. At the bottom left, you’ll see the option to go back to the Start screen with the tiles:

Now how about closing those open apps? Well, it’s a continuation of the two methods I have shown above. When you move your mouse to the top or bottom left corner, if you have open apps, you’ll see a very small outline alone the left side:

Now if you simply move your mouse pointer down towards those outlined apps, a whole bar appears and you can see all the open apps:

Now you can simply right-click on any of the Metro apps and choose Close.

This is totally not something I would have figured out on my own, so I’m guessing this will make a lot of people mad. Now that I’ve gotten used to it, it’s kind of nice not to have the taskbar around. I have been using OS X Lion for a while now and the full-screen apps are really handy. However, in Lion, you can simply move your mouse to the bottom or side and see all your open apps. It would have been nice if they had defaulted it to show the entire bar instead of having to first move the mouse to a corner and then move it down to see everything else.
So there you have it! An entire post on how to close an app in Windows 8. Enjoy!