why does romeo compare juliet to the sun

Romeo compares Juliet to the sun to express that she is the source of light, warmth, and life in his world. This metaphor highlights Juliet's beauty and radiance, portraying her as the center of his universe who outshines everything else, even the moon, which represents anything less beautiful or less significant to him. Romeo sees Juliet as a force that transforms the darkness of night into the brightness of day, symbolizing how she brings happiness and hope to his previously sad and lonely life. This comparison also emphasizes the intensity and power of his love for her, as Juliet's presence alone can "kill the envious moon" that pales in comparison to her brilliance.