Character Enhancements: Hero's that eat metal!
Galactus eats planets by converting them to energy.
Phoneix destroys life force as Dark Phoneix
Thanos is inorganic and would be my pick to start eating metal.
Wolverine with his bones and healing factor could probely get away with a little iron in his diet.
Silver Surfer, say in order to stay silver he has to start eating metal, sorta like Galactus has to eat planets.