Windows 8 Modern (Metro) apps use the full screen on your display regardless of how much of the screen they really need. As a result, that weather app, mail program or stock ticker is going to use the entirety of your computer display.
ModernMix is a new program from Stardock that lets you run Windows 8 "Modern" apps in a window on the desktop. You can also display and pin Modern apps on the taskbar and close Modern apps by clicking its close button.
You can test a beta version of ModernMix for 30 days. The price of the application is $5 which is quite nominal.