Never seen a metal bong (unless you mean a can)... but anyway thats definately a real general question, i mean buying a bong is kind of a personal preference for aesthetics and just how you like to smoke. If it's your first one i would suggest getting an inexpensive one, because you might break your first one three days after you get it (personal experience). Or go with a pyrex one, which is basically plastic. I would say just get a small water bong at the local smoke shop, maybe with an ice twist for a cool smoke. And if you dont have one already, buy a pipe first.