VGC, to my knowledge, only ever lets Pokémon caught/hatched within the most recent region to be allowed to participate. However, Melmetal inherently can't abide by those rules due to only being available in Go. Is Melmetal doomed to be unusable, will they make an exception, or will they let you catch one in the DLC? I really hope its not the latter since I had to transfer the only one I had in Go to Home