Omnimon is the Digimon that results when WarGreymon and MetalGarurumon DNA Digivolve together to create a stronger Digimon.
His body is entirely covered in white armor adorned with black, blue and yellow markings. His left arm ends in WarGreymon's head and his right arm with MetalGarurumon's, giving him two primary attacks (Transcendent Sword and Supreme Cannon). The cape he wears flows over the width of his body.
His first appearance is in the second Digimon Adventure film, Our War Game!. WarGreymon and MetalGarurumon had tried unsuccessfully to defeat Diaboromon, a Digimon they followed into the Internet to prevent him from consuming all its data. When Tai and Matt were accidentally transported inside the Internet they gave their spiritual energy to their Digimon so that they could win - Omnimon formed and defeated Diaboromon.
In the second Digimon Adventure 02 movie, Revenge of Diaboromon, Omnimon reformed when the DigiDestined discovered that Diaboromon survived the first battle and returned to the Internet. Omnimon destroyed what he thought was Diaboromon but found that the battle had been a trap - he had been fighting a decoy that exploded to reveal the innumerable Kuramon that were sealed inside. After wreaking havoc in the Real World all of them fused to form Armageddemon, who Omnimon fought, but when he used his surpreme cannon to blow a hole in his forehead, he just shot out laser whips from the hole that defeated Omnimon. He gave his energy to Imperialdramon Fighter Mode (a more powerful version of Imperialdramon, the Mega Digimon formed when Veemon and Ken Ichijouji's partner Wormmon DNA Digivolve), who permanently destroyed Armageddemon when he Mode Changed into Imperialdramon Paladin Mode.