William Shakespeare's Romeo and Juliet is entirely poetic. Besides the sonnets found in the Prologues of Act One and Act Two, and the meeting of Romeo and Juliet for the first time in Act One, Scene 5--"If I profane with my unworthiest hand...." (ll.88-112)--the remainder of the play is written entirely in blank verse, unrhymed iambic pentameter [where each line usually contains ten syllables and every other syllable is stressed].
In addition to the blank verse and sonnets, Shakespeare employs much light/dark imagery. For instance, Romeo speaks of Juliet in images of light: "Oh, she doth teach the torches to burn bright (I,v,41), and Act Two is replete with light images in Romeo's balcony monologue:
But, soft! What light through yonder window breaks?/It is the east, and Juliet is the sun!'Arise fair sun, and kill the envious moon,/Who is already sick and pale with grief/That thou her maid art far more fair than she. (II,ii,2-6)
Friar Laurence, also, has a soliloquy spoken with light/dark imagery:
The grey-eyed morn smiles on the frowning night/Checkering the eastern clouds with streaks of light/And flecked darkness like a drunkard reels/From forth day's path and Titan's fiery wheels/Now ere the sun advance his burning eye/The day to cheer and night's dank dew to dry...(II,iii,1-6)
In addition to the beautiful use of imagery, Shakespeare employs other figures of speech such as metaphor, simile, personification, alliteration, and allusion. In Friar Laurence's soliloquy, for example, there is a simile: "flecked darkness like a drunkard reels"; personification: "The grey-eyed more smiles," and "the sun advance his burning eye";allusion with the reference to Titan. Apostrophe is used when Romeo, learning of Juliet's "death," cries out to fate, "Then I defy you, fate!" (V,i,24).
Poetic to the end, the play finishes with the speech of the Prince who uses alliteration and ends with a rhyming couplet:
A glooming peace this morning with it brings
The sun for sorrow [alliteration] will not show his head...
Some shall be pardoned and some punished [alliteration]
For never was a story of more woe
Than this of Juliet and her Romeo. [last 2 lines=rhyming couplet]