Metro style apps have direct access only to their installed location and their application data store. They deliberately do not have direct access to other parts of the file system so they cannot alter the system without the user's consent.
They can receive brokered access to other locations via capabilities or pickers. This will provide the file data to the app via the StorageFolder and StorageFile objects and the app can stream the data from them. The app cannot directly access the referenced
files.
--Rob
