The name I keep throwing around as a comp for Melo is Ian Mahinmi. Defensive big who can come in off the bench and protect the rim for 15 minutes. Probably doesn't stuff the stat sheet, but can nonetheless be a useful rotation player.
Melo has the tools to be more than that, but I want to see him show a working knowledge of fundamentally sound basketball before I start expecting more. His hands worry me, but I wonder if his deficiencies in that area are caused by a childhood of soccer. Maybe they get better with practice and repetition. Until/unless they do, he'll always be a poor rebounder and finisher for his size.