Answer :
Mercutio: the young Petrarchan lover. An audience favorite because he is a showstopper. Mercutio is a showstopper. He's dirty, funny, out of control, and—we'll say it—compared to him, Romeo and Juliet can seem whiny and repetitive. Mercutio is technically a minor character, but his personality has such a disproportionate impact that maybe he has to die or he would take over the play. In fact, English poet John Dryden said that Shakespeare himself admitted that he had to kill Mercutio—or else, he said, Mercutio would have killed him. HIs death is so important because Mercutio is portrayed as the middle character who links the play to different people and scenes. Shakespeare might have wanted him to be more of a friend to Romeo in the play. Mercutio helps in some aspects to confuse the audience. E.g. when he is dying, he says it is a scratch yet he is actually dying. Also, he curses both the families. The audience were not expecting this because firstly, he is a friend of both families and secondly, they would not have known that the hatred of both families killed Mercutio. Mercutio's death is so important to the plot because it shows where the play changes from comedy to tragedy as a main character, Mercutio dies. It is also important because from this point, the characters change and the mood is changed from being emotional to gloomy. Hope this helps! :)