In Romeo and Juliet, the feud between the Capulet and Montague families is relentless and even the servants of the respective households feel animosity towards the very mention of the opposing family's name. Despite Benvolio's attempts to prevent a fight, Tybalt reveals the intensity of the hate when he says to Benvolio, "...peace! I hate the word, as I hate hell, all Montagues and thee" (I.i.68-69). Benvolio encourages Romeo to attend the Capulet ball as Rosaline with whom Romeo is infatuated has been invited. No Montague is invited and so Romeo will accompany Mercutio, his friend who is also invited. Mercutio is related to Prince Escalus who will ultimately help the families repair their rift but too late for Romeo or Juliet.
The audience is first introduced to Mercutio in Act I, scene iv when he and Romeo are making their way to the Capulet's to attend the ball. Mercutio tries to relieve Romeo's depression as he is weighted down by his worries over his unrequited love for Rosaline. Mercutio gets quite excited when he relates the story of Queen Mab, a fairy queen and this is significant as it discusses how society is much like the fairy who is "no bigger than an agate stone" (53) and seemingly harmless. However, society is "tainted" (76), selfish and self-absorbed and even the reverend ("parson") looks to benefit himself much like the fairy whom he goes on to describe as a "hag" (92). Mercutio's words are clever, sharp and have double meaning and are intended to make the audience question the romantic ideals of Romeo and his fantasy and the reality of life. This is one of the reasons that he features in the play. He uses humor to bring the dark side to the forefront to ensure that the audience can have a better perspective and perhaps be forewarned of the tragic results of idealistic views which carry no sense of reality.
Mercutio's untimely death is further significant as it furthers the plot and catapults Romeo into a position in which he is jeopardizing any chances with his new-found love Juliet but cannot withdraw from this fight. Fate plays a major role in this play and with Mercutio dying it is as if there is no longer anyone to act as a foil to Romeo. Mercutio cannot therefore help Romeo manage his love for Juliet in a more realistic manner and the result is disastrous and absolute.
Many people say that mercutio was killed early in the play because Shakespeare realized that Mercutio would soon outshine Romeo in his wit and courage, and therefore would take attention away from Shakespeare's leading man. Mercutio is a great character for his humor, strenght, and devotion to Romeo. He is also perhaps the most eloquent speaker of all of the characters in the play.
Mercutio is funny, daring, and just awesome. He's a fighter and thinks of love as womanish. It was possible that he was killed off to show how much of a fighter he was, but it is also possible that Shakespeare was worried that he would be the star of the play. 'Sides, since when has a Shakespeareian Tragedy kept any of the characters you want alive? ^-^