Canned food is awesome but it can be murder on your all-too-finite metal supply. So I'm thinking it would be great if we could recycle cans.

Take the recipe for "food + metal = canned food" and turn it into "food + can = canned food." Follow that with a worktable recipe to turn metal into cans. Now it's a two step process: Stockpile some cans, then use them to can food.

When canned food is used in cooking, it now generates a meal plus a used can. A used can then be tossed into the smelter to get your metals back.