***I made this for myself but if you or someone you know would like this then be my guest. If I am wrong somewhere please share so that it can be corrected. Also, both Pokémon Let’s Go games will be released November 16th 2018. ***.
Transfer any pokémon from any of the two Pokémon Go to Pokémon Let’s Go games to obtain your Mystery Box. This will initialize the steps to catching meltan. Mystery Box is exclusive to each account.
Open box in Pokémon Go to start catching as many meltan as you can before the time sensitive Mystery Box closes. To reopen the box and restart the process of catching meltan again, you have to wait a set amount of time (one week) and send another pokémon to Pokémon Let’s Go.
Repeat Step 2 until you have enough candies to evolve meltan into melmetal which can only be done in Pokémon Go.