Merlyn's influence over the young Wart is largely positive in The Sword and the Stone. He challenges Wart's ideas about what makes a man great and what makes a ruler truly effective. By transforming him into different kinds of animals, he allows Wart to experience alternative philosophical viewpoints, broadening his horizons and allowing him to shape his own perspective on subjects such as war, honor, and courage.

As a teacher, he is patient and able to meet Wart on his own level, never browbeating opinions into his head or humiliating him into obedience. His comedic manner initially makes him seem an absent-minded professor type, but it helps make both Wart and the reader more comfortable in his presence.

Throughout the rest of The Once and Future King, Merlyn remains a great influence on Arthur's life, even as he disappears physically from the king's life. The lessons he imparts to Arthur help the king establish the principles of Camelot. Merlyn becomes a kind of symbol of Arthur's childhood once he disappears from the story, representing the lost innocence of Camelot. (The story takes a darker turn in The Candle in the Wind, when Camelot's fall is inevitable, and Arthur thinks back on his youth.)