If you want to close Moder UI apps (Metro apps) in Windows 8 you have two ways to do so. First, you can open the Windows Task Manager with Ctr-Shift-Esc, find the apps that you want to close and kill the processes in the task manager. Second, you can move the mouse cursor to the very top of the screen until it changes into a hand, hold down the left-mouse button then, and move it all the way down to the bottom of the screen.
Both options are not that straightforward, and there are certainly users out there who may prefer a faster way of closing Modern UI Style apps in Windows 8.
The free portable application Close Threshold for Metro Apps makes closing apps on the start page more comfortable. What it basically does is reduce the way you have to move the mouse down before the app gets closed.
You still have to move the mouse to the top and hold down the left mouse button, but instead of having to move the mouse then to the very bottom of the screen, you only have to move it down a little bit for the same effect.
The program starts with the default system settings active. What you need to do is reduce the threshold from its maximum value of 1000 to a lower value. This value determines the way that you have to move the mouse down to close it. Settings are available for both mouse and touch gestures
Keep in mind that a too low threshold value may make it more difficulty to move apps to the left or right side of the screen, a too high value would mean that you have to move the mouse further down before it gets closed.
You need to click on the save settings button before the changes become active. This will kill and restart the explorer process so that a restart is not required. And if you do not like the changes, you can at any time click on the reset button to reset to Windows 8′s default settings.