De acordo com Wikipédia :
Magneto has been frequently depicted as able to resist all but the strongest or most unexpected of telepathic attacks. A number of explanations have been proposed for his unusually strong resistance to telepathy, among them ... technology wired into his helmet (the explanation given in the X-Men film series and several comic plotlines)
Por outro lado, existem fontes que reivindicam que , nos quadrinhos, ele instalou circuitos de controle mental em seu capacete, mas a resistência é toda natural ou o resultado de seus poderes:
Magneto seems to have some “natural” resistance to telepathic intrusion, and over time his force of will has augmented his natural and learned telepathic defenses. In the past, Magneto has also shown himself capable of Astral Travel and passive empathic sensitivity.
....
During the Silver Age, Magneto did install technology into his helmet which allowed him to control other's minds. This was seen in (Uncanny) X-Men #18, and again the X-Men vs. Avengers miniseries in 1987. However, there is no hint or statement in the 616 that Magneto inserted tech into his helmet to block telepathic attacks, nor has he ever seemed concerned when his helmet is removed in a telepath's presence.
A Marvel Wikia afirma que o capacete o protege:
The helmet Magneto wears may be what contributes to his ability to resist all but the strongest or most unexpected of telepathic attacks, achieved due to technology wired into the helmet itself.
Também parece ser canônico explícito nas continuidades Fox, Marvel 1602 e Ultimate que é o seu capacete que fornece a resistência.