I hear that making aluminum cans by recycling old aluminum cans only requires 5% or 20%, (like I said it’s hearsay), of the the resources necessary to pruduce the same cans from ore.
I may be off in my figures, but since it takes less resources to melt down existing metals than to mine, smelt and refine from ores, wouldn’t the survivors of The End Of The World As We Know It have an easier time producing metal from the detritus of The World As We Know It than their ancestors had building TWAWKI?