Contrary to the name of the song, this song is actually not taught to Link by Princess Zelda. It is taught by Impa, Princess Zelda’s guardian. Zelda’s Lullaby is used throughout the game to “identify Link as having connections to the royal family”.
Link will need to use it at many points throughout the game, primarily when there is a Triforce on the ground, and this includes any time you reach a Great Fairy’s Fountain.
