Meltan often uses its unique physiology to express itself in unexpected ways
Meltan without its head
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 metal, which it does to absorb the metal. It can generate electricity using the metal it absorbs, and then fire 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.
It is the only Pokémon that can't have an origin mark from the core series. It can only legitimately have the Pokémon GO origin mark, as it has never been made available through gameplay or events of a core series game.
They are the only Pokémon in Pokémon: Let's Go, Pikachu! and Let's Go, Eevee! whose Kanto Pokédex number (152) is not the same as its National Pokédex number (808). While KantoPokédex numbers are normally used throughout the game, the judge screen displays National Pokédex numbers, which is evident for Meltan and Melmetal.
They are the only Pokémon officially introduced in Generation VII that are not in the Alola Pokédex.
They are the only Pokémon obtainable in Pokémon: Let's Go, Pikachu! and Let's Go, Eevee! that cannot have the Let's Go origin mark.
They are the only Pokémon in the National Pokédex of Pokémon GO and Pokémon HOME (Nintendo Switch only) to not be listed in a region section. Instead, they are put into "Unknown" and "Unknown Origins", respectively.
They are the only Mythical Pokémon that can be traded or placed in a Gym as a defender in Pokémon GO.
In the anime, Professor Oak is the person who gives Meltan its species name.
According to Junichi Masuda, Meltan and its evolution were created for Pokémon: Let's Go, Pikachu! and Let's Go, Eevee! out of a "desire to build a bridge between players of the core Pokémon series and players of Pokémon GO", to make both groups happy.
In a 2018 GameSpot interview, Junichi Masuda mentioned that Meltan was designed by someone "who was also a fan of the original games and played them as a kid".
Two people were credited as "Pokémon Character Designers" in Pokémon: Let's Go, Pikachu! and Let's Go, Eevee!: Misaki Hashimoto and Hironobu Yoshida. However, Yoshida has worked on the Pokémon games since Pokémon Yellow, implying that it was Hashimoto that designed Meltan.
Meltan is based on a hexagonal nut, and its tail resembles an exposed wire. Its lower body is based on gallium, a metallic element with a relatively low melting point of about 86 °F (30 °C). Gallium is used to make semiconductors, and can easily "attack" other metals, such as aluminium and tin, to form alloys that are either very brittle or liquid at room temperature. These may be referenced with Meltan's liquid body, electric affinity, and ability to absorb metals.
Meltan may also be inspired by mercury, a metallic element that is liquid at room temperature. Much like gallium, mercury can also conduct electricity, as well as react with many other metals to form alloys known as amalgams.
Meltan may be a combination of melt, metal, and たん -tan (diminutive Japanese suffix). It may also be derived from molten.