May is a Pokémon Coordinator from Petalburg City in the Hoenn region. She is the daughter of Norman, the Petalburg Gym Leader, and his wife Caroline, and she has a younger brother named Max. Her character design is based on the female protagonist from the Pokémon Ruby, Sapphire, and Emerald video games. At the start of her journey, May had little interest in Pokémon and agreed to become a Trainer mainly as an excuse to travel and see new places. Her first partner Pokémon was a Torchic, given to her by Professor Birch after a chaotic first encounter with Ash Ketchum and his Pikachu, which destroyed her bicycle. May quickly attached herself to Ash's group and was later joined by her brother Max, who traveled alongside them.

May's personality is cheerful, kind, and energetic, with a strong sense of curiosity and a love for food and shopping. She is emotionally expressive and can be a bit naive at times, which sometimes leads her into trouble or makes her an easy target for deception, particularly from the rival Coordinator Harley. She has a competitive streak and does not like being underestimated, though she rarely initiates conflict. May is also very family-oriented, caring deeply for her younger brother Max despite their occasional bickering, and she looks out for him during their travels. She has a somewhat dramatic and romantic side, enjoying stories, beautiful scenery, and sentimental moments. Initially unsure of herself and lacking confidence in handling Pokémon, she gradually becomes more self-assured through experience and the support of her companions.

May's primary motivation is to become a top Pokémon Coordinator, a goal she discovered after witnessing a Pokémon Contest for the first time in the town of Slateport. Before that, she had no clear direction for her journey. The Contest format, which emphasizes beauty, style, and coordinated performances in addition to battling, captivated her. She dedicated herself to training her Pokémon for these competitions, aiming to win ribbons and qualify for the Grand Festival, the championship event for Coordinators. Her ultimate ambition is to become a top Coordinator on par with the best in the field.

In the story, May serves as a traveling companion and close friend to Ash Ketchum during the Hoenn region arc of the Pokémon anime, which is also known as Pokémon: Advanced Generation. She and her brother Max join Ash and Brock for most of their journey through Hoenn and later through the Kanto Battle Frontier. May's role is that of a fellow trainer who grows from a hesitant beginner into a skilled and confident Coordinator. Her journey provides a parallel narrative to Ash's Gym challenges, focusing on the world of Pokémon Contests. She also acts as a caring older sister figure within the group, offering emotional support and occasionally mediating between the more impulsive members of the team.

May's key relationships include her bond with Ash, whom she respects as a mentor and friend, often admiring his battle instincts and dedication. She shares a sibling-like dynamic with Brock, who provides guidance and care during their travels. Her relationship with her younger brother Max is central to her character, as she learns to balance her responsibilities as a sister with her own goals as a Coordinator. She develops several rivalries in the Contest circuit, most notably with the elegant and competitive Coordinator Drew, who initially dismisses her but later becomes a respected rival. Another significant rival is Harley, a scheming Coordinator who holds a grudge against May and frequently tries to sabotage her performances. These rivalries push May to improve her skills and develop her own unique style.

Throughout the series, May undergoes considerable development. She starts as a reluctant traveler with little knowledge of Pokémon and a tendency to complain. Over time, she gains confidence, learns the value of hard work and perseverance, and becomes a genuinely skilled Coordinator. Her early failures in Contests teach her humility and the importance of preparation. She learns to trust her instincts and her Pokémon, evolving from a timid beginner into a charismatic performer capable of impressing audiences and judges alike. Her growth is reflected in her team's evolution, with her Torchic eventually becoming a powerful Blaziken through shared battles and training. She also learns to handle setbacks and betrayal, particularly from Harley, which helps mature her judgment.

May's notable abilities lie primarily in her talent as a Pokémon Coordinator. She has a keen sense for creating visually appealing combinations of moves and for presenting her Pokémon in the most flattering light during Contest appeals. She is creative in battle, often devising improvised strategies that leverage her Pokémon's unique traits. Her teamwork with her Beautifly in particular is highlighted as exceptionally harmonious, allowing for fluid and captivating performances. As she matures, she develops a reputation as a rising star in the Contest world, eventually being referred to as the dancing princess of Hoenn by some fans. She also has a natural knack for making Pokéblocks, and her homemade treat, May's Delicacy, is especially beloved by her Munchlax. Her perseverance and ability to learn from defeat are among her strongest personal traits, allowing her to keep improving and ultimately compete at the highest levels of the Grand Festival circuit.