What Happened To Everyone Who Used Cerebro?
2. Erik Lehnsherr
Erik Lehnsherr, AKA, Magneto and Cerebro have a long and complicated history. He helped design the computer alongside Professor X, but that's not the full extent of his interactions with the powerful device. Because he worked on the engineering aspect of Cerebro, he found a way to integrate similar circuitry into his helmet to completely block psychic attacks.
This has been demonstrated on numerous occasions in the comics, but also in the movies and television series. Magneto's helmet doesn't just set up his style, it's actually very practical seeing as his greatest friend/for has one of the most powerful minds on the planet.
Aside from this, Magneto actually has some telepathic abilities of his own. In the comics, it's those powers that help to shield him telepathically more than the helmet, but he also has been able to use Cerebro himself, though this is more mentioned than it is seen throughout his publication.
In many ways, Magneto's use of Cerebro has been through the manipulation of others. In X2: X-Men United, he used another Mutant to manipulate Charles Xavier into nearly wiping out all humans after altering Cerebro for his own purposes, but he can take a more direct approach when it comes to using the device in the comics.