"Avatar: The Last Airbender" explores themes of friendship and loyalty through the strong bonds between the main characters - Aang, Katara, Sokka, and Toph. The show highlights how their unwavering support for each other helps them overcome challenges and grow both individually and as a team. The characters constantly demonstrate loyalty by standing by each other in difficult situations and putting their friends' well-being above their own interests. Additionally, the show emphasizes the importance of trust, communication, and forgiveness in building and maintaining strong friendships.