Much of Romeo's character is on display with this line. The idea of setting up the look in Juliet's eyes and "twenty of their swords" helps to enhance the fundamental conflict in the romance of the two young lovers. Romeo is poised between difficult and competing ends in the look in her eyes and the swords that represent her name. At the same time, Romeo is trying to convey how he values her, Juliet, more than anything else. The language of "peril" in a look that she gives him is interesting. This "look" can be one of disapproval, reluctance, hesitation, but it is something upon which Romeo places heavy weight. The idea of Romeo's impulsive behavior and his propensity for hyperbole is also evident in this statement. The fact that Romeo claims through language that he is willing to ensure "twenty of their swords" to one look from Juliet helps to convey both his indulgence in emotions and his hyperbolic and intense view of the world. This is a sign to both Juliet and the reader/ audience that Romeo's roller- coaster of emotions can dip into the realm of the destructive, something that foreshadows what is to come in the drama.
The context for this quote is the balcony scene in the second act of the play. Romeo, thunderstruck with love for Juliet, climbs a high orchard wall and calls her to her bedroom balcony, where he speaks to her from below.
Juliet, who knows Romeo is part of the hated Montague clan, fears that if he is discovered by any of her relatives, they will kill him on the spot. Romeo, heady with love and full of bravado, responds with a swaggering statement:
Alack, there lies more peril in thine eyeThan twenty of their swords. Look thou but sweet,And I am proof against their enmity.