Romeo and Juliet is not a poem but a full-length play by William Shakespeare. The play is written in two styles, however, prose and verse, and the verse could be seen as poetry since it adheres to a specific poetic meter (iambic pentameter). The most significant opposing imagery occurring in the play is that of light and dark, and a corresponding set of images referring to the sun, moon, and stars also appears.
Juliet is referred to by Romeo using images of sunlight ("It is the east, and Juliet is the sun / arise, fair sun..."), whereas Juliet uses moon imagery when speaking to Romeo ("O, swear not by the moon, th' inconstant moon, that monthly changes in her circled orb"). This is interesting because traditionally in literature the sun is thought to be masculine and the moon is thought to be feminine. This contrast underscores not only the uniqueness of their attraction but also its instability; it is as if the world is turned upside down and the natural order of things is challenged. Since the story became one for the ages, a classic example of romantic enduring love, Shakespeare's imagery was well chosen.
Stars are a frequent motif also (the opening speech by a narrator refers to the "star-cross'd lovers," which means astrology and fate are not in their favor). Juliet muses on Romeo as she looks at the night sky, waiting for him, and says, "when he shall die, take him and cut him out in little stars, so all the world may be in love with night." The emphasis on darkness and night refers to the secrecy of their love but also underscores a sense of opposition: they value the beauty of night over day and find the darkness a welcoming, rather than a frightening, place. It might also serve as a foreshadowing of their deaths.