The sun, the moon, the stars..

Imagery helps the audience feel and imagine what is going on the the text. Throughout the play, there are references to the sky. The main idea of Romeo and Juliet being 'star-crossed' lovers means that they were brought together by the stars, in other words their star signs mean't that they would be a match.
At the beginning of the play, Romeo is deeply depressed because of Rosaline, and he is found wandering the night by himself. He is introduced into the play as a dark person. This all changed when he meets "Juliet..the sun" ( scene 2 acts 2). Juliet brings him out of the dark and into the light, she is his reason to be happy.He also says that "O! she doth teach the torches to burn bright" (act 1 scene 5), Juliet has taught him that the world is not a dark place and the only way he will move on from such a state of depression.
The references to the sky show the audience that Romeo is a very spiritual being and he is deeply influenced by his heart. His feelings take over the logic of the whole idea, in this case, she doesn't seem to think of what would happen if he marries a girl that he just met the day before.The sun burns bright like Romeos passion, and relating the couple to the sky was a very good way that Shakespeare engages the reader.
"The brightness of her cheek would shame those stars, as daylight doth a lamp; her eyes in heaven”(II, ii, 19-20) Romeo means that the brightness of her cheeks would outshine the stars the way the sun outshines a lamp. If her eyes were in the night sky, they would shine so brightly through space that birds would start singing, thinking her light was the light of day.
Romeo places juliet on such a high pedestal, and relates her to the sky yet again, this time saying that her beauty is greater than that of the sky. She illuminates the dark and everyone and everything around her is affected.