“Metal roofing” covers more than one kind of roof. Concealed clips and standing seams behave differently from panels fastened through exposed washers. The building, slope and intended appearance help determine which system fits.
Metal moves as its temperature changes. The attachment and transitions need to accommodate that movement while keeping water outside. Pipes, valleys and connections to lower roofs deserve as much attention as the long straight panel runs.
A detached garage may have a different roof pitch, interior use and condensation concern from the house. Treating each building as its own roof helps avoid choosing panels by appearance alone.