It is the last Pokémon in the National Pokédex as of Let's Go, Pikachu! and Let's Go, Eevee!.
It was officially revealed on October 24, 2018.
Melmetal is a large silver Pokémon with a roughly humanoid build. It mainly consists of a liquid metal that is reflective. Many large dark gray hexagonal nuts appear on its body, including its shoulders, elbows and hands, one in the middle of its chest, and one on each foot. A gold-colored nut makes up its chest and second one serves as its head. Much like Meltan, it has a grey orb that serves as its pupil and a small red tail.
Melmetal was in known in ancient times to be worshipped for the ability to create metal. Its body is incredibly sturdy due to evolving from combined Meltan. Due to the state of its liquid metal body, the arms are very flexible, capable of delivering power punches.