metal would be preffered but MUCH harder unless you are good with welding or have a bunch of shit you can screw together to make a good one. Most (home made bongs) are plastic with some other material for the bowl. It must NOT be plastic. I think most have plastic basins, plastic or metal downstem and a metal bowl. A socket from a socket rench works well for a bowl. And a metal tube for downpipe and soda bottle for basin. It will be heavy so don't let it tip. ANd make sure you are using safe metals