"when things become as bad as they are bound to get, and people have grown stunted and deformed by their overwhelming negativities, Maitreya (or Metta) will show himself. Although fully enlightened, he won't appear as a Buddha at first. He'll simply show up as someone taller and more attractive than everyone else. Impressed by his beauty, people will ask him how he got to be so good looking. He will reply, "Through the practice of morality, avoiding giving harm to any living being."
-----------------------------------------------------Buddhism for Dummies