It doesn't and it cant not by breeding or tutoring.
Never without cheats or hacks.
Chat with our AI personalities
It will if you obtain it in a trade.
on level 53
Yes, you can have a level 50 Metagross with Meteor Mash. you have to trade it to your Pokemon Diamond/Pearl/Platinum through Pal Park. Pal Park opens up after you receive the National Pokedex. (On your DS game...) It learns Meteor mash at level 55. However you can still make a metang not evolve (by pressing b during evolution or giving it an everstone.) and make it learn Meteor mash at level 50 and only let it evolve at 50 (it usually evolves at lv.40)and then you will have a metagross with Meteor mash at level 50.
Aggron can learn earthquake by using the TM on it.
meteor mash