Question: why tybalt and mercutio fight?
Answer: Romeo protests that he has good reason to love Tybalt, and does not wish to fight him. He asks that until Tybalt knows the reason for this love, he put aside his sword. Mercutio angrily draws his sword and declares with biting wit that if Romeo will not fight Tybalt, he will. Mercutio and Tybalt begin to fight.