Hello
@xstxphoenixx! I am a newer player as well, but I've played metagross fairly consistently over the past few months and managed to take home some CP at all of the IRL events I have attended, so I'll offer up my two cents.
As for its place in the current meta, it's unfortunately a bit underwhelming at the moment, mostly due to its damage cap. Back when it took 2nd place at Madison regionals last year, the format was dominated by 170-180 HP Ex's and basic Gx's, which made it a phenomenal stand alone attacker. Since the release and recent successes of golisopod Gx and zoroark Gx, one-shot decks need now need to be able to hit 210 damage consistently to be competitive. This means metagross needs help in the form of supplemental attackers like necrozma Gx, mimikyu, or solgaleo Gx, which in turn hinders the consistency of the deck. I'd call it solidly tier 2 in a streamlined solgaleo list, but most lists I've seen have it as tier 3 or off the radar entirely. That being said, I think it is super fun to play, and more consistent than people give it credit for if you build it correctly!
Volcanion matchup is actually quite simple to tech against, though I wouldn't recommend sacrificing consistency for it at a big event. If you are at a smaller/local event and you expect to run into a fire deck or two, I would play a 2/1 line of alolan ninetales with luminous barrier, a single basic water energy and professor's letter so can search it out with skyla. If they don't run oranguru you should actually be slightly favored...just target down their baby volcanions and the rest of their deck literally can't do any damage, so you just aurora beam until you take 6 prizes or they concede. The element of surprise is obviously very helpful here, I had a lot of fun with this matchup at a local league cup back in November! Alternatively, mimikyu with a choice band would also be good for return KO's on turtonator Gx and ho-oh Gx, but it still sounds like a losing matchup to me at that point.
As for zoroark, I tested the combo rather extensively online, as there is actually quite a bit of synergy between the two cards. Trade provides draw support while also helping you get energy in the discard pile for geotech, and riotous beating is solid two shot attack that is easier to stream/abuse max potion with compared to metagross' giga hammer. Unfortunately, I never felt comfortable with a zoroark heavy list, as I always struggled to keep up with more straightforward zoroark lists that were able to start 2-shotting faster and more consistently than I was, and at made the gardy matchup a bit shaky due to always giving up at least 2 prizes to guzma/gallade. So for Memphis regional, I decided to trim the zoroark line and go all in for OHKO's with a 2/0/2 solgaleo Gx inclusion. Despite not having much time to test the concept or refine the list, I piloted the following deck to a 4-1-4, top 256 finish:
4/2/4 metagross Gx
2/0/2 solgaleo Gx
1/1 zoroark Gx
1 alolan vulpix (the one with beacon, obviously
1 magearna Ex
2 tapu lele Gx
4 N
2 sycamore
3 brigette
3 guzma
1 skyla
4 ultra ball
4 max potion
4 rare candy
3 choice band
2 field blower
1 rescue stretcher
1 professor's letter
7 metal energy
1 psychic energy
In hindsight, the only changes I would have made to the deck would be to swap the rescue stretcher for a super rod to help draw into energy late game, and to drop one of the choice bands for a dhelmise to help deal with buzzwole. Energy count seems low initially, but it's actually pretty easy to skyla/professor's letter for it when you need it. Everyone knocks the consistency of running two different stage 2 lines, but alolan vulpix, algorithm Gx, and skyla are so good at helping setup that it usually isn't that big of a problem. My main issue with the deck is how slow it is...I didn't finish 3 full games once in my 9 rounds at memphis, and all the ties cost me a shot at advancing to day 2.
As for ultra prism, there is a lot of metal support, though it remains to be seen if metagross itself will stay relevant. Most obviously, dusk mane necrozma Gx plays the same role as solgaleo while being a basic, so that should help in a vacuum. But there is also a metal energy accelerating magnezone coming out which may be a faster/more consistent method of powering it up. The new solgaleo prism star is also possibly worth a look as it is a bulky single prize attacker, does 10 more damage than metagross, and can help accelerate energy under ability lock or late game after a metagross gets KO's. Those are my thoughts, I hope you find them helpful!
