A mask covers your face. In
Future's song "Mask Off",the mask symbolizes the cautiousness or unwillingness that he has go show all the true colors of his past and his personality. Mask on is symbolic of a fake or incomplete version of who he is. Mask on is him being cautious about what he shows about himself. He says, Fuck it, mask off, meaning that he is letting it all goshowing his fans his complete and true self.