The X-Men send Wolverine to the past in a desperate effort to change history and prevent an event that results in doom for both humans and mutants.
Past spoilers alert.
Once upon a time, there were two timelines for the the X-Men: One in the “current” time, where Professor X is, actually, Captain Picard and the “past” time, where Professor X is actually an assassin. Well, at some point of a series, there is this need of “merging” things (sometimes with sad results, like when Asimov merged the Robots series with the Foundation series. But that’s something for another time).
Anyway, that’s what this movie is: try to merge both timelines in a single, coherent timeline. It falls short in the second part, but it’s entertaining to see them trying anyway.
To merge those two timelines they came with a new “ex machina” in the form of Kitty Pryde ability to transport people’s “conscience” to another time (dunno if it is an ability she has in the comics, but I never saw something like that in the previous movies). She can send people’s memories back in the time, to the same body, to the same person. Kinda like full time travel, but only inside one’s timeline.
(Weird how they gave Kitty, a mutant that can transport solid objects through other solid objects the ability to send something immaterial through time, another immaterial thing.)
So what they do? They send Wolverine, which can withstand prolonged time travel without burning all his brain cells, to prevent the death of Mystique and give the Sentinels the power to defeat all mutants. And that’s basically it. And being a blockbuster, you basically already know how this ends.
One thing that everyone is mentioning and I need to add my voice to it is the Quicksilver scene, in which he defeats a whole group of guards in a confined space. It is a brilliant scene to show his powers — beyond the “he’s fast”. Also, it reminds me a lot of “The Ballad of Barry Allen” which, although being about Flash, it shows somewhat how speedsters must feel.
Even if the scene kills it, Even Peters doesn’t seem into the role. Probably because his character just shows up, do his thing and then goes away, without ever being mentioned again (he appears in one of the last scenes, but meh). Everyone else is still the same: Did you like James McAvoy as Chavier? Good, you’ll like him here; did you like Patrick Stewart as Chaver? Good, you’ll like him here. And on, and on.
Again, it is entertaining, even if you need a big “ex machina” to make things work.