As with desktop programs, you can pin a Metro app to the taskbar. If a Metro app is running, it'll have an icon on the taskbar, too.
And as with desktop programs, if you hover your mouse over a taskbar icon, a thumbnail of the Metro app appears. For some apps you will also see fully functional miniature media controls, as in the illustrated Xbox Music app. (No, there's no volume control.)
Store appears on the taskbar by default.
To banish Metro apps from the taskbar, right-click any empty spot on the taskbar; choose Properties; and under the Taskbar tab, uncheck the box marked Show Windows Store apps on the taskbar.