Windows 8 ships with several built-in default Metro or Modern Apps. These are called Provisioned Apps.

Provisioned apps are staged in the image itself and are scheduled to be installed for every user of the Windows 8 image at first logon. No way, they can be removed from the image - as it may create issues during installation.

You can add these apps to a Windows image when you boot into audit mode before you deploy the image by using the DISM app provisioning commands. Provisioned apps are specific to the PC and will not roam with the user.

You can only install 24 provisioned apps in an image.

Source: TechNet.