Meltan

Meltan is a small Pokémon with a silvery body of liquid metal. Its head is hard and resembles a golden hexagonal nut, with a small black sphere floating inside. This sphere serves as its eye. It has a red tail that resembles an electrical wire with two tiny protrusions at the end. According to official concept arts, Meltan's liquid body is made of gallium, and it can cry gallium tears. Its arms can stretch to be longer or shorter.

Meltan's body can corrode various metals, which it then absorbs and eats. The absorbed metals are circulated within Meltan's body to generate electricity, which it uses as an energy source. Meltan can also use this electricity to attack by firing it from its eye. According to Professor Willow, Meltan has been described in ancient texts found in the same place as the Mystery Box, a mysterious item that attracts Meltan to its location when opened. Professor Willow also states that Meltan is said to be created from small shards when a Melmetal rusts and splits apart. Meltan is known to live in groups, until the day comes where one strong Meltan absorbs the group to evolve into Melmetal.

As seen in the anime, the hexagonal nut on Meltan's body can be removed. It has also been seen working in packs. When provoked, it will spin its head, creating a sound that calls others of its own kind. This head-spinning can also be used as a sign of affection. The anime has also shown that Meltan can be tamed if fed metal-like treats, and it can multiply in numbers overtime. Meltan is one of the smallest Pokémon, tying with Alolan Diglett and Klefki as the shortest Steel-type.

Evolution
Meltan evolves into .

(Source: Bulbapedia)