How powerful will meteor mash be?

Steel types is only effective against Ice, Rock, & none existent presence of fairly types. Even if it is the best steel type move ever created it will have limited use.

Best case scenario: it's the steel version of Frenzy Plant. Worst case scenario: it's the steel version of Psycho Boost. I'm honestly hoping it's a two-bar move (Metagross doesn't need any more one-bar moves) that at least outperforms Heavy Slam.

Best case senario- New gym defender with the CP rebalance and best counter for Xerneas and Tapu lele down the line

Steel licks. Question answered.

I expect whatever it ends up with will be enough to make him meta-relevant but only of occasional use. His stats are ridiculous, his typing is pretty cool, but they can't OP him too much because he resists 10 types, 2 of them double. I expect a steel Future Sight-level. Strong enough to be useful, but hampered by a single bar to compensate for how hard it will hit.

There was this article, sizing up its performance in any case where Meteor Mash becomes better than Flash Cannon: https://pokemongo.gamepress.gg/october-2018-community-day-metagross-time-shine

My hundo is itching to be evolved and I have a healthy supply of Pinaps to burn through. An hour of trades after for lucky rolls and I hope to have at least a few of these monsters worth dusting once all is said and done.