When I am travelling around Africa and especially Nigeria, there are two very obvious sources of metals and I'm amazed that nobody bothers collecting them: the first is that the equivalent of several years' GNP is hanging in tatters from all the telegraph poles in the form of massive tangles of copper telephone cable, now disused. Before cell phones arrived, the telephone was a nightmare and NITEL used to just come and string a new cable to your house or office (once you'd paid the special "service charge" and the hire of the ladder and bought the wire, both of which had actually been stolen from NITEL, obviously) adding more and more weight until sometimes the poles, weakened by termites, would just fall over wiping out the entire district.
The second is a bit less obvious: when you are stuck in traffic and gazing vacantly out of the car window and your eye falls to the road surface you realise that the road is peppered with millions of metal bits that have dropped off cars and trucks, been squashed into the hot tarmac and then polished by millions of tyres passing over them, creating a rather attractive and completely random artwork of shiny shapes, most unidentifiable, gleaming from the black tarmac. If somebody just went round with a big magnet and a digging tool they could collect thousands of tons of metal from very short stretches of road. Labour being Africa's cheapest commodity, I'm surprised that nobody has thought to collect these metals and export them to China. I guess the certainty of being killed by the same traffic is what puts people off both sources.