Some times we might have installed lots of apps and games. All these will be included in Metro UI screen. We can reduce the size of the icons and save space. We can uninstall any app/s from this screen.
Step 1: Open your metro screen by either clicking on
windows logo button on your keyboard or by clicking on
windows start menu button.

Step 2: Now select the
icon which you prefer to reduce the size. Now
right click on the file which you had selected. On performing this, a small tool bar will appear on your screen, as shown in below image.

Step 3: In this tool bar click on
smaller button and observe the size of the icons. Similarly you can repeat these steps and save space in metro UI.

Step 4: To increase the icon size. Repeat all the steps and now instead of smaller button you will get
larger button. Click on this button to increase the icon size.
source:Windows tips and tricks/technoon