When Sabretooth reports to Magneto after his failed attempt to capture Rogue, Magneto is using his powers to suspend a set of five marbles over his desk and manipulating them into acting like a mutant version of a Newton's Cradle. He continues to toy with the marbles through the rest of their conversation before eventually letting them clatter down onto the desk when he leaves the room. It is unknown whether these were simply 'toys' or would have been used as improvised weapons should the need arise.
Following the events of X-Men, Magneto is incarcerated in a prison designed specifically to not contain any metal whatsoever. Mystique seduces Magneto's prison guard Mitchell Laurio while he's off-duty and injects him with liquefied iron. When Laurio returns to work the next day, Magneto kills him by extracting the iron from his blood. He then shapes it into several marbles, and flattens one of them into a disc to stand on, and uses the rest to shatter the prison and free himself.
Before lifting of RFK Stadium, Magneto attempts to retrieve his stolen helmet. Possessing two steel marbles as weapons, he enters the Pentagon, knocks out two guards and a clerk, and retrieves his lost helmet.
- Unlike X2, where Magneto extracted the iron from Laurio's bloodstream in order to form the marbles, it is unknown how Magneto came across the marbles he possessed in Days of Future Past. They could've either been formed or stolen.
- In the script, after extracting the metal Magneto forms it into a giant ball, and he grabs onto it as he floats out of his cell.