In Act III,scene i of Romeo and Juliet, Tybalt, Juliet's cousin has picked a fight and Romeo, being aware that he is Juliet's cousin, wants to avoid the confrontation as "I...love thee better than thou canst devise."(III.i.67) Mercutio, on the other hand, is happy to fight and draws his sword against Tybalt. Tybalt, is quite prepared to fight Mercutio and agrees "I am for you" and draws his sword. 

Shakespeare has structured the scene to build the tension and these words of Tybalt's have been used before in Act I scene i line 52 when Sampson says it as he incites the Montague servants and a fight ensues. It reveals that the feelings of hatred between the two families run deep, even extending to the servants. Tybalt's willingness to get involved in a fight is also evident.  He hates any "talk of peace" (I.i.67); in fact, "As I hate hell, all Montagues,..."(69) whereafter he fights, reveals his impulsive nature, preparing the audience for his actions later.

In terms of dramatic technique, Shakespeare leaves his audience with no doubt about what follows these words - a fight! The meaning is therefore enhanced. The fight in Act III however will have far-reaching consequences and, whilst the words are short and to the point "I am for you," the audience is alert to Tybalt's impetuousness. After Tybalt fatally wounds Mercutio, the turning point of the play will follow shortly when Romeo kills Tybalt to avenge his friend's death and there is no going back for Romeo.