Pokemon TCG: Melmetal-GX Box - Rules of Play says:
What an amazing discovery! The newly discovered Mythical Pokémon Meltan and Melmetal are stepping into the spotlight in the new Pokémon TCG: Melmetal-GX Box. This collection includes foil cards of these astonishing Metal-type Pokémon and all the power of a Pokémon-GX. Plus, tear into 4 Pokémon TCG booster packs to expand your collection!