Meteor is the king of the Dragon Legions which make their home at Fort Draco, which was once Mossdeep city.
You first encounter him in the Solar Caverns, after the gym leader Haruko sends you there to investigate, where he challenges you to a battle. This is caused by his rage at you being alive, and breaking the contract you had sealed with him earlier. His team is a solo Lv. 22 Dragon.
After you defeat him, he leaves the Caverns, and is absent for quite a while in the ROM. However, he is mentioned quite often, especially when you invade the Weather Institute by Fortree city. In this Institute, Meteor's daughter is held captured by Gleis and his Zombie Legions. Once you rescue her, your goal is to return her to him.
Meteor reappears once again as he assists you during the invasion at Lilycove city against Chloe. His followers, Visigoth and Hun, defeat and devour the footmen assisting her, and take you to Fort Draco, where he and Dr. Blackthorn are waiting to be reunited with her. As thanks, Meteor gives you the HM02 Fly.
Meteor also appears as the Gym Leader of the Fort Draco training gym. This time, his team is a Lv. 52 Altaria, a Lv. 53 Dragon, a Lv. 50 Dragon, a Lv. 48 Dragon, a Lv. 51 Kingdra, and a Lv. 48 Dragon. Any Ice- or Dragon-type Pokemon will easily crush his team.
Upon his defeat, Meteor bestows to you the Knight's Emblem, a symbol of you officially becoming a Trainer Knight.
He appears once more at the meeting after you get through the Abandoned Mine with Dr. Blackthorn. He joins your party to break into Sootopolis and rescue Landon and May.