Usage patterns
〈物〉が金属でできているsomething is made of metal
This watch is made of metal.
金属を加工するto process/work metal (e.g. shape or machine it)
They are processing metal at the factory.
金属を溶かすto melt metal
They melt the metal at high temperatures.
金属音がするto make a metallic sound
A metallic sound rang out when the door closed.