Its appearance was first teased during the September Pokémon GOCommunity Day on September 22, 2018, and it was officially revealed on September 25, 2018.
Meltan is a small Pokémon with a shiny, silvery body made of liquid metal. Its head is a golden hexagon with a large circular hole in its center, resembling a hexagonal nut. Floating inside the hole is its eye. A red tail extends from its body with two tiny protrusions at the end.
It is a curious and expressive Pokémon. Meltan's liquid arms and legs can corrode and absorb metal into its body, which it uses to generate electricity. Its eye can use this energy to fire an attack against opponents. Meltan are instinctively drawn towards each in order to combine into Melmetal.
Many Ditto transformed into Meltan have been observed in Pokémon GO, including in Professor Willow's field work. It has also 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. As seen in the anime, Meltan can travel underwater.
Multiple Meltan have made a number of appearances in the Sun & Moon series. Three appeared in SM106, where they were briefly seen underwater, simultaneously marking the species' debut. Multiple Meltan were then seen inside the cargo hold of the ship that Ash and his classmates took back to Melemele Island at the end of SM109. They will appear in SM112.
Meltan is currently the only Pokémon capable of evolution that cannot be evolved in the main series games.
Meltan may be based on a hexagonal nut, and its tail resembles an exposed wire. Its body is based on mercury, a metallic element that is liquid at room temperature. Mercury can also conduct electricity, as well as react with many other metals to form amalgams.
Meltan may be a combination of melt, metal, and たん -tan (diminutive Japanese suffix). It may also be derived from tantalum or molten.