Never used metal ones, 'cause they'll rust (unless you paint them with a Rustolium-like product, and they seem like they'd transfer heat & cold. I have used whiskey barrels for dogs, screwing the bands in place so they don't loosen as the wood shrinks. Lots warmer & cooler than metal You'd have to wire-brush the insides, though, unless you like drunken ducks. You could also use a large igloo-type dog house, should work wellhas anyone made a coop/house out of a 55 gal metal oil drum? I have TONS of the stupid things. I was thinking i would use one for the ducks my hubby doesn't know about yet