Mercutio uses Tybalt's sword-fighting skills as a metaphor for his character, dismissing his fashionable and precise style because he lacks spontaneity and creativity when he fights. Mercutio also states that Tybalt's precision stems from the desire to claim insult and demand a fight so that he can show off, then turns a phrase about Tybalt's use of French to imply that he has a French venereal disease instead.
Mercutio derides Tybalt extensively and viciously. Although he acknowledges that Tybalt is a skilled swordsman, he attributes those skills to education and a desire to look good rather than any natural talent or inclination.
In Act 3 Scene 1 of "Romeo and Juliet," Mercutio antagonizes and provokes Tybalt, who is seeking Romeo. When Romeo arrives, Tybalt demands to fight him; when Romeo refuses, Mercutio takes up the sword instead and the two duel. As Romeo attempts to halt the fight and puts himself bodily between the two duelists, Tybalt stabs Mercutio and flees.
Romeo and Mercutio have two different reactions to the sudden violence and death. Romeo curses fate for forcing him to fight Tybalt, Juliet's cousin, and reinforces the atmosphere of tragic destiny that permeates "Romeo and Juliet." However, Mercutio dies cursing the Montagues and Capulets for their feud, instead of cursing Tybalt.