With the arrival of mutants into society, Victor von Doom realized humankind was behind the genetic curve. In order to raise himself above his genes, Victor studied ways to advance himself technologically and mystically. He succeeded in creating a Liquid Metal he could use as a body armor and manipulate into weapons.
Instead of fighting Magneto during the Mutant-Human War, Doom offered to fight by his side. Realizing that mutants were obviously the next step in human evolution, Doom wanted to be on the winning side of the war-and he was. Doom became Magneto's most successful ally. Although neither of them truly trusted each other, each man respected the other's powers and abilities.
After the mutant victory over the humans, Doom took over the nation of New Latveria. He eventually married a woman named Valeria and had a child, Kristoff; he transformed them into the superhumans Invincible Woman and the Torch, respectively. They, along with the monstrous It, form the Fearsome Four. The group is used as a strike force by Magneto to keep other superhumans in line. It is a position Doom would prefer not to be in, but with the amount of mutants in the world, and the power Magneto has over them, it would be unwise to lash out in frustration. Especially with no concrete plan laid out for victory.
Recently, Doom's frustration at being seen as Magneto's human lapdog has caused him to question his relationship with the House of M. How, and if, he decides to sever that relationship has not been decided.