Little is known about Junkpile except his former affiliations and the hatred they produced in him towards the X-Men
's leader, Xi'an Chi Xan. When Xi'an was convicted of murdering casino boss Noah Synge, Junkpile jumped at the chance to get even. Junkpile and Xi'an were formerly members of an outlaw group known as the Lawless until Xi'an decided to "go straight" and clean up his act, leaving the group. During the skirmish that followed, Junkpile mercilessly killed Serpentina
--an elastic mutant who had joined the team--while he was trying to get to Xi'an.
Later, when Skullfire and La Lunatica set out on their own, Luna contacted Junkpile to help her stay safe from the hunters that the Theatre of Pain had set out to retrieve her. Skullfire had great difficulty with this partnership, as he still harbored feelings of resentment against the villain for killing Serpentina. The trio soon stumbled upon the lair of the Driver, a mysterious mutant smuggler from the old days, along with Xi'an. The Driver intended to transmute the DNA of the group into a data stream so that they could be preserved until a utopian golden age came, starting with Junkpile. The group was saved by the malevolent intervention of Brimstone Love, the leader of the Theatre of Pain. After being freed, Junkpile charged after the Driver, who commanded his car to ram Junkpile. The car has the ability to phase through solid objects, and upon phasing through Junkpile, caused a seizure in him. Junkpile started telekinetically pulling all pieces of machinery, including the Driver's computer, towards him, destroying the data of all the mutants that the Driver had stored. Xi'an used his healing powers to restore Junkpile, but only so that he would owe him a favor in the future.
His disassembled body was found months later by President Doom and Morphine Somers, who wanted to use the mutant as a weapon against the X-Men. They put him back together and offered him a membership to SHIELD
, giving him complete autonomy to do his bidding. Junkpile jumped at this chance and formed a squad called the Junkyard Dogs to attack the X-Men. Instead of going after his enemies, he found his way to Death Valley, where, trapped with Skullfire, actually teamed up with his hated enemy in order to escape the machinations of the Theatre of Pain.
Junkpile has a unique techno-organic physiology which allows him to construct his body entirely out of metal. This grants him with increased strength, stamina, and resistance to physical injury. He also has telekinetic abilities so that he can draw and bond metal objects to himself to add to his body or rebuild himself when destroyed.