Who he is: Magneto, a.k.a. Erik Lehnsherr
His power: Magneto can manipulate magnetic fields with his mind, which allows him to control all metal, fly, and create a magnetic shield around his body.
His story: Magneto is the tragic antivillain at the center of the X-franchise, and both X-Men and X-Men: First Class begin with a young Erik being separated from his parents when he’s put in a concentration camp in Auschwitz. Eighteen years later, Erik hunts, interrogates, and kills ex-Nazis as he searches for the man who killed his mother in the camp, and he joins up with Charles Xavier and the CIA to wipe out their mutual enemy in First Class. After assuming the role of Magneto, Erik splits off from Charles and creates his own mutant brotherhood with Charles’ childhood friend Mystique, but that group won’t last when the U.S. government starts coming for it. Erik is framed for the assassination of John F. Kennedy when he’s actually trying to save the president, who is secretly a mutant, and put in a glass prison under the Pentagon in X-Men: Days Of Future Past.
This is where Magneto’s story splits in two. In the original XMU timeline, Magneto eventually gets out of that prison and reconnects with both Charles and Mystique. He helps Charles recruit a young Jean Grey in X-Men: The Last Stand, but he’s back in a more antagonistic role in X-Men, where he fights against mutant-registration legislation by creating a machine that causes fatal genetic mutations. Charles’ X-Men defeat Magneto, and he ends up in yet another glass prison, and in X2, Maj. William Stryker visits that prison and forces Magneto to give up secrets about Xavier’s School. Magneto escapes with Mystique’s help, and they join forces with the X-Men to stop Stryker’s plot to kill all mutants. Magneto gains a new brotherhood in X-Men: The Last Stand, which he uses to take down Worthington Labs after it announces the creation of a mutant cure. He abandons Mystique when she’s exposed to the cure, and he leads a small army of mutants that storms Alcatraz Island, but Magneto is ultimately removed from the fight when he’s exposed to the mutant cure himself.
The cure removes Magneto’s powers, but they’re back by the time he reappears in X-Men: Days Of Future Past to help the X-Men as Wolverine tries to change the course of history. He succeeds, and that’s where the second timeline comes into play. Freed from prison, Magneto hijacks Bolivar Trask’s mutant-hunting Sentinels and tries to kill President Nixon on the White House lawn. Mystique stops him, and a decade later, Erik has created a new life for himself with a new wife and daughter in Poland. His new family is killed, and he’s recruited by Apocalypse to become one of his four horsemen, giving Magneto a significant power upgrade, which allows him to destroy what remains of Auschwitz. Magneto helps Apocalypse at first but eventually realizes that destroying the world is a pretty shitty thing to do, so he turns on his new master and wipes him out with Jean Grey’s help.
Played by: Brett Morris (child) in X-Men; Bill Milner (child) in X-Men: First Class; Michael Fassbender (adult) in X-Men: First Class, X-Men: Days Of Future Past, and X-Men: Apocalypse; and Ian McKellan (older adult) in X-Men, X2, X-Men: The Last Stand, The Wolverine, and X-Men: Days Of Future Past.
Currently, Magneto is: Back to his regular power levels and off on his own, though his relationships with Charles and Mystique have been renewed.
Where will we see him next? Magneto will always be a presence in the XMU, but there are no future appearances planned for him at the moment. Fassbender’s three-picture contract expired with X-Men: Apocalypse, so the role may need to be recast if he decides not to don Magneto’s helmet.