Pokémon GO network traffic has revealed the National Pokédex numbers for the new Mythical Pokémon Meltan and its evolution, Melmetal. Meltan is officially #808 and Melmetal is directly after at #809. The Pokémon Company is expected to formally address these new numbers soon, so stay tuned for any updates. Melmetal can only evolve in Pokémon GO but can be transferred to Pokémon Let’s Go Pikachu and Let’s Go Eevee.
New Mythical Pokémon Meltan and Melmetal confirmed as numbers #808 and #809 on the National Pokédex
Pokémon Blog 