A poster of the show

The series explored many concepts rarely touched on in western children's television shows, including issues relating to war, genocide, and imperialism, gender discrimination and female empowerment, marginalization and oppression, and the philosophical questions surrounding fate and destiny.

The show is set during a period where the entire world is engulfed in an imperialistic war initiated by the Fire Nation. While war is a constant backdrop, the show depicts these effects through the eyes of common people—the oppressed Earth Kingdom citizens as well as brainwashed Fire Nation schoolchildren—to show how war makes victims of everyone. And while the Fire Nation is presented as the instigator of violence, the show also depicts the systemic inequality experienced by residents in the Earth Kingdom city of Ba Sing Se as well as the nefarious activities of the city's secret police. These situations show the corrupting nature of power and the nuances of good and evil. The show introduces viewers to genocide early on when protagonist Aang visits his former home in the Southern Air Temple. He arrives to discover his people have been massacred, and allows him to display a range of emotions, from rage to loss.

The character Zuko and his relationship with his father and Uncle Iroh is the series' main redemption arc and represents the show's message that destiny and fate are not binding or set by other people, but can be changed. In season one, he struggles to conform to the destiny and path determined by his father, but Iroh prods him, asking, "who are you, what do you want?" The show also represents a diverse cast of characters in order to tackle the issue of marginalization. For example, in introducing a blind character like Toph and a paraplegic boy like Teo, the show depicted characters with vulnerabilities overcoming their physical and societal limitations. This is also true when it comes to the show's female characters. For example, female protagonist Katara faces systemic sexism when she reaches the Northern Water Tribe to learn waterbending. In another instance, her brother, Sokka is initially dismissive of the all-female Kyoshi Warriors, but learns to respect and appreciate their skills. According to Kirk Hamilton of Kotaku, these themes represent the show's message that it's more important to be yourself than to hew to the roles society expects of you."