Romeo and Juliet and Twelfth Night are both very popular works by William Shakespeare, and share a number of his literary techniques.
Shakespeare, as both playwright and poet, uses rhyming couplets to great effect, emphasizing the point made in the second line, as the rhyme adds more impact when spoken.
Fate, show thy force; ourselves we do not owe.
What is decreed must be; and be this so.
Romeo and Juliet:
My only love sprung from my only hate!
Too early seen unknown, and known too late!
He also uses a contrast of verse and prose. Verse is more poetic, usually appearing in a regular rhythm of 10 syllables, while prose is more like spoken language where the words run across the page and seem more "real." He often uses verse to identify more upper class characters such as the Duke in Twelfth Night, and prose for lower class characters, and to highlight serious and more humorous topics. Blank verse, or iambic pentameter, is a strong feature of Shakespeare's writings in general.
Puns, or plays on words, are used frequently. In Romeo and Juliet, note the play on the word sole.
Not I, believe me You have dancing shoes with nimble soles.
I have a soul of lead so stakes me to the ground I cannot move.
In Twelfth Night one example is when Orsino’s servant Curio asks the duke if he wants to go hunting the “hart,” a male deer. “Why, so I do, the noblest that I have,” replies Orsino, referring to his actual love-sick heart.
Metaphors are also used frequently in Shakespeare, in particular extended metaphors. In Romeo and Juliet there are many links to light and dark as a metaphor for good and evil.
The brightness of her cheek would shame those stars,
As daylight doth a lamp; her eyes in heaven
Would through the airy region stream so bright
That birds would sing and think it were not night.
In Twelfth Night he uses numerous nautical metaphors, which are particularly apt as the play begins with a shipwreck that lands our heroine Viola on the shores of Illyria.
O spirit of love, how quick and fresh art thou,
That notwithstanding thy capacity
Receiveth as the sea, naught enters there,
Of what validity and pitch so'er,
But falls into abatement and low price
Even in a minute.