The idea of using a galvanized garbade can sounds better than the actual followthrough. Many have thought about that and the idea of the galvanized metal always raises a red flag with some king of metalic poisoning. Use caution!
Sounds like what you really want is a Cajun Mocrowave. Below are a couple of links of some you can buy but, if you look closely, you can figure out how to build one yourself. Or you can just do more research and get more info on building one yourself.
The next one is the Cadillac of Cajun Microwaves.