So, Meteor mash is "overpowered"
As i predicted it might be.
https://pokemongo.gamepress.gg/q-a/how-powerful-will-meteor-mash-be
It's actually on par with frenzy plant rather than my blast burn prediction, but both frenzy plant and blast burn fall into the category of "overpowered" community day moves.
Is this a good choice? While it will take Metagross very high up the DPS charts, this is arguably offset by steels poor usefulness offensively. Plus the lack of snow, unless you're from Norway, Siberia or Greenland.
Good luck catching your shinies and high IV metagrosses.
Answers
According to your words, Meteor Mash will probably skyrocket Metagross up the DPS charts, with a massive Atk stat of 257. You might say Steel is a poor offensive type, but remember that Steel is one of the two only types that are SE against Fairy(and let's just say that Metagross with MM will just outperform every single Poison-type).
Counterpoint, while Steel may not hit effectively most of the time, it roasts Gardevoir and Clefable, common Machamp walls, while resisting their attacks. It's also good against the big 4, resisting Blissey's entire moveset, and same for Chansey, AS WELL AS Snorlax's Heavy Slam, Body Slam, Zen Headbutt and Hyper Beam. It also resists Slaking and Donphan's Play Rough, Tyranitar's Stone Edge, and the list goes on. Furthermore, it makes a great choice in a generalist team featuring Dragons, covering all their weaknesses. (At least the ones we currently have) And don't forget Meteor Mash is ridiculously good with STAB, even though it doesn't hit for SE damage most of the time.
Before this, Metagross was as disappointing as Gyarados without a water fast move. Then he gets waterfall, and bam, best non-legendary water attacker by a wide margin. Most people loved that Gary got a water move. Now that Metagross is getting a good Steel charged move, why all the doom and gloom? Looking forward to seeing Metagross on the Pokebattler and GamePress best counters lists.
Because a pokemon's meta-relevancy shouldn't be dictated by a move only obtainable on a single day. It makes missing out feel even worse for those that have work or other obligations that day.
To make matters worse, if you're one of the unlucky ones who evolved a Metagross before its community day, you're stuck with trash cannon.
I, for one, am glad to see Metagross cut its way to the top as our new steel overlord. It was always a top pick in the main series, so it was kinda sad seeing how mediocre it was in Go (due to lackluster charge moves).
With MM, Metagross becomes an incredibly strong option without being broken or overpowered. It will make for a top-notch generalist with high neutral DPS and TDO as a result of a great stat spread and fantastic typing/resistances. It will also make for a much stronger gym defender, given that it will fire off MM far more frequently than it would it's other charge moves.
That said, it won't outperform specialist attackers and will be a bad pick against fire, water, electric, and other steel Mons. MM finally gives Metagross some much-needed meta relevancy without making it too stupidly good.
We have to remember that Metagross is fantastic in the main series, often in the top tiers of competitive play, not surprising and if somebody deserved it, he certainly fit the bill. You could say every Gen has one Pokémon that breaks out of their “could be useful but movesets” phase. Gyarados was one, Ttar is kind of arguable since he was still useful. Metagross was hardly used at all and now he’s been placed somewhere where he should belong. The stats he has shouldn’t be out of a top 10 for SE damage against anything
Dragonite has reigned in this game for what seemed like an eternity until Rayquaza showed up - both on Gym offense and Gym defense. Tyranitar was king of Mewtwo and Lugia raids as well as others including the Latis, and after its Community Day became the absolute ruler of the Legendary Birds as well as a high-tier gym defender. I don't see anything wrong with giving Metagross high neutral DPS and king of underused Steel-types. After all, Dragonite still hits more things for Neutral damage and has a better defending Quick move, and Tyranitar is still pretty relevant come Giratina raids (which will devastate Rayquaza Mewtwo Latios and Gengar with SE 3-bar Charged Moves)
