(.85)^4 = 52.2% of Meteor Mash hitting 4 consecutive times.
Considering your 85% accuracy, you have a 17% chance of getting an attack boost each time Meteor Mash is used.
(1-.17)^4 = 47.5% chance of getting an attack boost over the course of 4 Meteor Mashes.
Just did that to put things into perspective and show how Metagross can handle Cresselia rather well when you look at it from a 1v1 standpoint. But yes, what Dozz says still stands. Of course, since you are running TR most Cresselias aren't too threatening with their speed alterations (Thunder Wave, Icy Wind) and STAB Psychics (can vary depending on what you are running). TR-Reversing Cresselias could pose a problem, though this most likely means that your opponent is running slow mons as well.
EDIT: Also remember that Iron Head is a viable option if you are concerned about Meteor Mash's accuracy.
Considering your 85% accuracy, you have a 17% chance of getting an attack boost each time Meteor Mash is used.
(1-.17)^4 = 47.5% chance of getting an attack boost over the course of 4 Meteor Mashes.
Just did that to put things into perspective and show how Metagross can handle Cresselia rather well when you look at it from a 1v1 standpoint. But yes, what Dozz says still stands. Of course, since you are running TR most Cresselias aren't too threatening with their speed alterations (Thunder Wave, Icy Wind) and STAB Psychics (can vary depending on what you are running). TR-Reversing Cresselias could pose a problem, though this most likely means that your opponent is running slow mons as well.
EDIT: Also remember that Iron Head is a viable option if you are concerned about Meteor Mash's accuracy.