Meltan

Meltan is an enigmatic Steel-type Mythical Pokémon. It evolves into Melmetal when fed 400 candies.

Trivia

 * Most of Meltan's body is made from liquid metal, and its shape is very fluid. It can use its liquid arms and legs to corrode metal and absorb it into its own body.
 * Meltan generates electricity using the metal it absorbs from outside sources. It uses this electricity as an energy source and also as an attack that can be fired from its eye.
 * Clearly a curious Pokémon, Meltan is very expressive and shows an interest in all kinds of things.
 * It was originally unavailable for capture, but it appeared in the wild as a disguised Ditto.
 * Its name was originally displayed as "???" in gameplay and in game data it is referred either as "Pokémon 891" or "Kecleon", the second one was because of Meltan being initially released in the game by replacement of Kecleon assets before its own were added to game files.
 * Additionally, following names were given for this Pokémon in player community before its official name was announced: "Nutto", "Nutface", "Incogditto", and “DittoNut”. All of these nicknames refer to either its nut-shaped head or its resemblance to Ditto.
 * Its small, silver body resembles Ditto and a hardware nut-shaped head with an eye floating inside, which when displayed in nearby as shadow silhouette resembles Unown.
 * It cannot be rotated in the encounter screen and in the official gameplay, there is no possibility to have it in screens such as Pokémon summary page, Pokédex entry nor Buddy Pokémon screen and in the Map View its model's scale is incredibly small, however using AR+ or third party software to manipulate gameplay its rear can be seen with a little red wire tail visible.
 * In case of shiny variant this tail has a blue color.
 * It is the first and only Pokémon to debut in Pokémon GO before any other Pokémon game, including main series.
 * Before Melmetal have been revealed there were speculations that Meltan would have an evolution form, as there were sound files in game data hinting it as well as mysterious shadow at the end of Pokemon Let's Go: Meltan Evolution Teaser Trailer.
 * There are sound files of Meltan's and Melmetal's cries in game assets. These files are called "pv891.wav" and "pv892.wav" and they implied that Meltan's National Pokédex entry number could be 891, which could confirm at least 86 new Pokémon species introduced in Generation VIII of the core games series, however after final release of this Pokémon to the game its Pokédex number was revealed to be #808.
 * Eventually, trainers will be able to obtain Meltan when they transfer a pokemon from Pokemon Go to Pokemon Let's Go. It will give them a mystery box which they can open and Meltan will appear for that player only.
 * It is one of the 4 pokemon that require 400 candies to evolve.
 * Meltan candies can be acquired by sending Meltan from Pokémon GO to Pokémon: Let's Go.
 * Meltan is the only Mythical Pokémon that can evolve.