Angor was a world of chaos. Metahumans were fighting in the streets, with little regard for the safety of one another, or even awareness of the innocent bystanders their brawls killed. So the hero known as Tin Man did the unthinkable - he ran for US President on a platform of metahuman control. When he was elected, he brought the heroes together. From now on, they would save the world. However, the heroes were stuck - many metahumans did not want to have to join the Meta Militia, and these were placed in conditions similar to those of a concentration camp. This issue, among others, led to the creation of the subversive group called the Extremists, who struck first when their leader, Lord Havok, killed Tin Man during a live broadcast.
The Meta Militia continued to safeguard and make the world a "better" place for several years, until the arrival of Monarch's Army , who recruited them in a massive strike against the Extremists. Unfortunately, this resulted in the deaths of most of the Meta Militia, except Americommando, who was rescued (and arrested) by Bluejay. The last status of the team was unknown, but is factible its disbanding.
Post-Flashpoint, the Metamilitia was displaced by the Retaliators.
The Meta Militia was an analog to the Avengers-The initiative from Marvel comics. In the post-Infinite Crisis continuity Angor was rebranded earth-8. Isn't clear if previously to the existence of the Meta Militia there were a post Infinite Crisis version of the Champions of Angor.