Alexander Summers is the younger son of Christopher and Katherine Summers, and younger brother to Scott. Christopher was a test pilot for the air force, and was flying a private plane with his family on board when the plane was attacked by a spaceship from the Shi'ar Empire. There was only one parachute, so Katherine strapped it to Alex and Scott before pushing them out of the plane. Both boys survived the crash and, since it was believed that their parents were dead, they were adopted separately.

When Alex was attacked as a teenager, his mutant powers surfaced. Raging out of control, his plasma blasts accidentally incinerated the boy who was attacking him. Mr. Sinister, who had been monitoring Alex ever since he was adopted, placed genetic locks on Alex to stop him from developing his mutant powers again. As a side effect of the blocks, Alex also forgot what had happened and how he had killed a boy.

Alex remained unaware of his mutant powers until he graduated from college. He was captured by his archeology professor, Ahmet Abdol and experimented on. Alex's mutant powers resurfaced under the strain of Abdol's technology, alerting Professor Charles Xavier of his existence. The X-Men arrived t rescue him and Alex was reunited with his older brother; the X-Men's field leader, Cyclops.

Since Alex was still incapable of controlling the shock waves his body emanated, he chose to remain in the Egyptian desert rather than accompany the X-Men back to their headquarters in upstate New York. However, Alex was soon captured by a mutant-hunting robotic Sentinel and taken to the headquarters of Larry Trask. Trask gave Summers the codename "Havok" and a costume with helped him regulate his powers.

When the X-Men freed Trask's captive mutants, Havok finally accompanied his brother and his teammates back to civilization where the X-Men began training Alex to help him keep his energy in check. Eventually, Havok gained enough mastery over his power that he would release it only when he wished to do so, and could wield his power skillfully enough to become a formidable opponent in battle.

While with the X-Men, Havok fell in love with Lorna Dane, the mutant known as Polaris. They both served for a time in the X-Men helping to repel the invasion by the alien Z'Nox. Neither Havok nor Polaris wished to lead a life as an adventurer, but they discovered that they had a mutual interest in geophysics. The duo left the X-Men and returned to school. Havok and Polaris later joined the Pentagon-sponsored mutant team X-Factor. After X-Factor disbanded, Havok later returned to the X-Men.