The movie is just a recap of the TV series. 
A.D. 1982, the planet alignment brought the human beings ordeal we should overcome, and it caused a convulsion on the Earth. During the conflict, a light fell on to the Myojinsho reef, and five lights scattered around the Earth as if they followed it. 
17 years had passed since then. A.D. 1999, human beings had developed all of the solar system, and began to embark for outer space. The Earth Defense Army organized an elite squad, Crasher, to provide for various happening in space. Myojin Takeru was the member of the team. He was found in the light fell on to the Myojinsho reef. Actually he was Mars who was born on the planet Gishin. When he grew up, he heard unearthly voice, 
“Mars, stop the Earthians’ advancement to the space. Explode the Earth” 
He was a living triggering device that had been sent by Emperor Zure, who plotted to conquer the universe. However, Mars, who had been raised as an Earthian, rejected the order, and made up his mind to face the severe fate. 
(Source: AnimeNfo)

Six God Combination GodMars: The Movie