Won't break if you drop it?
Other than that, you're bound to get a metallic taste out of any metal teapot (that isn't enameled, and most of them will be) that you use to make any tea with even a hint of acidity (most teas are somewhat acidic). The more reactive the metal (copper, silver, iron) the more taste. Of course, the tea cools off super fast in those as well, so it doesn't have much leach time.
I'd stick with glass for the best experience, though I've seen a number of restaurants use small stainless steel pots to good effect.