Melmetal

Great League: 3.5 / 5

Melmetal is a very promising and unique Pokemon in Great League, only limited by availability to owners of the Nintendo Switch games Let's Go Pikachu and Let's Go Eevee. If you don't have a Switch, it might be worth poking a friend or acquaintance that does have it, partly to the huge cost of just evolving Meltan. Melmetal's strengths in PvP are its excellent charge moves backed by a fast energy-generating Thunder Shock, allowing Melmetal to apply large shield pressure as a tanky Pokemon. Mono-Steel typing offers a wide range of resistances, but not being able to punch hard against the actual fighters (Medicham, Lucario, etc.) is somewhat discouraging.  Overall it definitely has its place in the meta, just keep it away from Counter users, the mud bois (Whiscash, Marshtomp, etc.), and Steelix. 

Ultra League 3.5 / 5

With a higher CP cap in Ultra League, Melmetal continues to show dominance in many of its matchups and remains a solid pick in this league. Being able to compete against top picks such as Lugia, Cresselia, and many of the Dragon-type pokemon here is definitely worth noting. The weaknesses to Fighting, Fire, and Ground haven't left it though, and this is where Melmetal struggles to gain an upper hand. 

Master League 4.5 / 5

Thanks to the CP restriction removed in Master League, Melmetal's out there flexing its big 3599 max CP in the form of its big fists. While it doesn't actually have its signature move yet, its current moveset is actually quite good, resulting in more wins than losses in this league. Bashing Kyogre, Cresselia, and Lugia is definitely fun for our big metal boi, but losing to Groudon, Lucario, and Giratina, ain't so hot. At the end of the day Melmetal will still perform very well, as long as you pick your battles accordingly.