Max is a genius in the theory of Pokémon training, but he was too young to receive a Pokémon when he first appeared. Both May and Max are the children of Norman, the Gym Leader of Petalburg City and his wife Caroline. The two have a very close relationship. They often get upset with each other, but when they are in dangerous situations they try to protect each other, especially May. She sometimes gets angry with Max because he knows a lot about Pokémon and she is annoyed by not knowing the basics of training or Pokémon. He decided to travel with Ash and May to see even more Pokémon.
When Ash arrived at the gym without May in Petalburg City, he was met by little Max who was surprised to meet a trainer who he had watched on television only weeks ago, through participation in the Johto League Silver Conference. But he also mocked him for losing in the quarter finals of the tournament. He also criticized the Pokémon May chose, Torchic, saying he would have chosen a Treecko.
During his travels with his sister and his friends, Max was in charge of May's PokéNav, acting as a guide. Later on in the series, Max makes a habit of pulling Brock's ear when he sees and talks to a pretty girl, halting his romantic advances as Misty did in Kanto and Johto and the way Croagunk would Poison Jab Brock in Sinnoh for similar effect.
In the movie Jirachi: Wish Maker, Jirachi partnered with Max, becoming his first Pokémon. In Do I Hear A Ralts?, Max rescued a Ralts that was hurt and took the job of returning it back to its family, Gardevoir and Kirlia.
In Battle Dimension, Max made a brief cameo appearance with his parents watching May compete in the Wallace Cup, and also appears in a photo in the second Diamond and Pearl Special Episode.