When you find the trees that grow springs, gears, and robot you can destroy them to get
metal essences

You can find them in a cave in the dessert.When you find them the option oil will come up
instead of water then you will know where the metal is.But first you need the flamethrower
which you will get once you have a four star town.Hope you find it!

this involves access to the desert and a blowtorch. Go to the really big door in the
desert. use the blowtorch to open it. You should be in a junkyard. Look for the cave
and there should be three metal trees in there. all you have to do is melt one (placed
there instead of chop down) and you get metal. Good luck

plant a plant that u have to oil example(gears/robots)