In Shakespeare's Romeo and Juliet, although Mercutio has the name most connotative of mood swings, Romeo is the character who is the most mercurial. Introduced as a almost Hamlet-like character who bemoans his fate in life, the victim of unrequited love who speaks in oxymorons, Romeo acquiesces to his loyal friend Benvolio's attempts to distract him, by attending the feast given for Juliet Capulet. Once there, he becomes the quintessential romantic who is dazzled by Juliet, who "doth teach the torches to burn." With the bravado of love, he recklessly, scales the walls of the Capulet orchard just to see "his love," whom he describes in metaphor and images of light.
Impulsively, then, after receiving Juliet's declaration of love, Romeo rushes to Friar Laurence's cell, demanding that the priest perform the marriage of him and Juliet. This assertive personality is exhibited later, after Romeo leaves the marriage bed of Juliet only to encounter the enraged Tybalt.
At first, Romeo tries to explain to Tybalt that he no longer harbors antipathy for him, but Tybalt does not understand and continues his duel with Mercutio, slaying him. Then, Romeo becomes disgusted with himself, saying he has become weak and "womanish." Enraged, he kills Tybalt to avenge the death of his friend Mercutio. However, when he learns that he is banished by the Prince, Romeo flings himself on the floor before Friar Laurence who accuses him of acting like a girl as he melodramatically exclaims that he will be in hell if he cannot be with Juliet.
In the last two acts of the play, Romeo loses his weakness in acts of defiance against fate as he returns to Verona in order to be with Juliet, even in death. Now a desperate man, Romeo slays Paris, whom he suspects of desecrating Juliet's tomb. Yet, there is one constant in this impulsive, mercurial character and that is his fidelity to his love, Juliet.