Even if you did have a cupola furnace that would melt steel, you'd want steel that was of a known castable alloy, not a mixture of whatever's in cans. And even aluminum cans, which melt at a much lower temperature, are poor candidates for remelting, since they have so much surface area - they mostly produce aluminum oxide and fumes from burning paint.
One creative idea, if you want to do something with your cans, is to make candle lanterns out of them. Fill them with water and freeze them, then use a punch to put decorative patterns in them, that the light from the candles can illuminate (once you pour out the melted ice).
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