The Magneto of the Amalgam Universe is a combination of Marvel's Magneto and DC's William Magnus.
Erik Magnus was born with the same powers (and fashion sense) of the Marvel version of the character. His brother is Will Magnus, who hated his brother for overshadowing him by being born with mutant powers. His brother created the Sentinels to hunt down all mutants.
After a tragedy that caused the loss of his Brotherhood of Mutants that scarred Magneto deeply, he created the Magnetic Men to help him in his quest to help and liberate persecuted mutants. He chose machines so that he would not have to face such a loss or have such a connection ever again. But he created them too well and eventually grew to care for them as he would any other person. They eventually gained sentience.
The Magnetic Men were killed in battle with the Impossible Mod, and Magneto sought to restore their lives. He was successful in reviving them and he had Mister Mastermind give them the ability to appear human. He then gave them human identities and disbanded the group, wanting them to live normal lives because he did not want to put them in harms way again.
He went in search of his brother in an attempt to stop him from further destruction to the mutant race. But he soon learned that the Magnetic Men were in trouble and went to their aid. He soon learned that the Magnetic Men are far more powerful in his presence, and they wished to remain by his side. The group reformed and also gained an ally in the Sinister Society, having a common enemy in Will Magnus.