Generally speaking, supply and demand.
The current spike in pretty much all metal prices is that Covid had caused some production problems as well as softened demand. So now demand is back but there is a delay as things ramp back up, causing a huge gap and spiking prices.
Plastics are tied to oil which is getting hit with freaking out over Texas, plus a ban on new drilling contracts, plus cancelling pipeline construction.
The current spike in pretty much all metal prices is that Covid had caused some production problems as well as softened demand. So now demand is back but there is a delay as things ramp back up, causing a huge gap and spiking prices.
Plastics are tied to oil which is getting hit with freaking out over Texas, plus a ban on new drilling contracts, plus cancelling pipeline construction.