Protagonists:
* Percy Jackson: The protagonist and narrator of the story. A 12-year-old boy who discovers he is the son of Poseidon, the Greek god of the sea. He is initially reluctant to accept his destiny, but eventually embraces it and sets out to clear his name after being accused of stealing Zeus' lightning bolt. Percy is brave, resourceful, and loyal to his friends.
* Annabeth Chase: A 12-year-old daughter of Athena, the Greek goddess of wisdom and warfare. She is a skilled strategist and fighter, and she is loyal to her friends. Annabeth is quick-witted, resourceful, and a strong leader. She acts as Percy's guide and friend throughout the story.
* Grover Underwood: A satyr who is Percy's best friend and protector. Grover is kind, clumsy, and often nervous, but he is fiercely loyal to Percy and always willing to help him. He is searching for Pan, the god of the wild, and believes Percy is the key to finding him.
Antagonists:
* Luke Castellan: A seemingly friendly, but actually villainous, son of Hermes, the Greek messenger god. He is the leader of the "Council of the Young," a group of demigods who are trying to overthrow the gods. Luke is cunning, ambitious, and ruthless, and he is ultimately responsible for stealing Zeus' lightning bolt.
* Ares: The Greek god of war, and the son of Zeus. Ares is a powerful and dangerous enemy who is angry at Percy for disrupting his plans.
* The Fury: A monster who is tasked with hunting down and punishing Percy for his alleged crime. She is described as having a terrifying appearance and is a formidable enemy.
Supporting Characters:
* Chiron: The centaur who is the trainer and mentor at Camp Half-Blood. He is wise, kind, and a skilled fighter, and he is a source of support and guidance for Percy.
* Mrs. Dodds: A fierce Fury who is actually a monster in disguise, posing as Percy's math teacher. She tries to capture him, but Percy escapes.
* Clarisse La Rue: A daughter of Ares who is a bully and rival of Percy. She is a strong and skilled fighter, but she is also arrogant and ruthless.
* Thalia Grace: A daughter of Zeus, and the leader of the Hunters of Artemis. She died as a child, but is now immortal thanks to her sister's help. She is a skilled warrior and is always ready to help Percy.
This is just a brief overview of the major characters. There are many other interesting and well-developed characters in *The Lightning Thief*, each with their own unique personality and motivations.