To smelt means to melt rock to get metal out of it.
Smelting is a way to make metal things. It is a very old way to make metal things.
Examples:
The workers smelt the rock to get the metal out.
We can smelt the metal from the rock.
The workers smelt the rock to get the metal out.
I smelt the rock and got a lot of metal!
In the old days, people smelt rocks to get metal for their swords and armor.
The workers smelt the rock and made a big sword.