Ok, so here is my view of what Melkor looks like after he's returned from the void. He's not wearing his old body, but a new one. This one is younger, slimmer, and only slightly shorter than his old one, but it is also weaker, but more flexible. He is very unhappy with it, at least at first, because it lacks the power he is accustomed to, and also because it's much more "mortal" than his was. Pain is more apparent(it's my headcanon that Valar and Maiar feel less pain than elves and men, they just don't register it), and it succumbs to hunger just like that of any elf or man. However he is still able to go longer than either race without food, and lift much more than another with the same build by almost twice as much.