Yes. Though logic suggests that your motorcycle is already covered when it’s parked in a garage, it’s always wise to put a cover over your motorcycle.
A cover will protect your motorcycle from dust, UV rays, and from getting scratched. Garages are usually all-purpose rooms, where people do anything from household chores to light engineering, so you’ll want to keep your motorcycle protected from anything that could happen, from accidental paint spillages to welding sparks! Luck favors the prepared!