In some indeterminate "now", a ragtag group of surviving mutants is engaged in some kind of epic battle with looming robots that bear an eerie resemblance to a certain metal titan that was the titular character of Brad Bird's The Iron Giant. The film pretty much plops the viewer down in media res, with something going on with Kitty Pryde (Ellen Page) and Bishop (Omar Sy), who remove themselves from the main field of battle to engage in some kind of activity that has Kitty cupping a blue energy field around Bishop's head. While this opening sequence fairly clearly details the fact that the giant Sentinels (which are in fact not metal, and are thus impervious to Magneto's "charms") are able to adapt to various mutants' abilities, offering near instant "antidotes" that allow them to keep the upper hand, the film can't quite escape some clunky exposition after things finally settle down and the basic setup is detailed by Charles Xavier (Patrick Stewart in this "current" timeframe). It turns out that back in 1973, Bolivar Trask had already built Sentinels with the express purpose of identifying and eliminating the then nascent mutants. Raven and/or Mystique (depending on what you want to call her) had infiltrated Trask's inner circle to kill him, but the government was waiting for her and she was captured. With her shape shifting DNA now available, Trask was able to re-engineer the Sentinels to be able to instantly morph themselves, making them basically impervious to any attack by a mutant's special powers. In other words, if Bobby Drake (Shawn Ashmore) uses his ice making capabilities to freeze a Sentinel, the robot can simply instantly heat up to melt the ice. What's a mutant to do?