Pastor Mike was the head of a small Christian congregation in Broxton, Oklahoma. When the Norse city of Asgard appeared over Oklahoma, this conflicted with their Christian belief system. It also greatly angered all the townsfolk. Mike would lead the people toward Asgard to tell the Asgardian Gods that they were no longer welcome in Oklahoma and they needed to leave. This would lead to multiple run-ins with Volstagg, who believed this to be an act of war.
This was all a prelude to the true battle at hand – Galactus had come to Asgard seeking the Worldheart. In order to watch over and protect the Worldheart, the Silver Surfer decided to remain on Earth and proposed that Pastor Mike become the new Herald to Galactus. The Silver Surfer hoped that Pastor Mike, as Galactus’ herald, might become the conscience Galactus needed to hopefully spare any life in his unending search for sustenance. This seemed to have worked as evidenced when Galactus decided to return to Earth to protect the Seed from being awoken by the Celestials.