I would think no, right? Like, let's say you put a polished steel can (with its convex surface) out in the sun. The reflective properties would reflex away the light and heat. It would also disperse it being a convex surface. Also, a metal being a pretty good conductor and only half the cylinder can be exposed to light at any given time, the heat energy will travel to cooler side of the can, the side in the shadow, making it harder to concentrate the heat to cook things.
Like, there's a portable
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that's just a concave/parabolic mirrored surface that reflects all the light and heat energy into a glass tube. If something like a glass oven to trap the heat AND a parabolic surface is needed just to cook a small amount of food, I would think Colossus needs way more than his metal skin.