Before the play even starts, Antonio and Shylock have a very antagonistic relationship. It drives the play’s most suspenseful plot elements. Antonio disapproves of Shylock’s financial practices and lends money free of interest, competing with Shylock’s moneylending. Shylock reports that Antonio publicly condemns his usury and hates him for being Jewish:
You call me misbeliever, cut-throat dog,
And spit upon my Jewish gaberdine...
And foot me as you spurn a stranger cur.
Antonio asks to borrow money from Shylock in order to lend it to Bassanio. Because Antonio is opposed to charging or paying interest, Shylock instead imposes a penalty if Antonio does not repay the sum within three months: he wants “an equal pound / Of your [Antonio’s] fair flesh, to be cut off and taken / In what part of your body pleaseth me.”
Shylock assures Bassanio he is joking, and Antonio is sure that he will be able to return the money on time. Unfortunately, both Antonio and Shylock have bad luck, and Shylock demands the pound of flesh. Shylock’s animosity towards Antonio makes it impossible to persuade him. Portia saves Antonio on a technicality, and the only one who suffers in the end is Shylock.
This relationship contributes much to the play. The bond enables Bassanio to woo Portia and then forces Portia to save Antonio for Bassanio’s sake. It creates tension as the audience worries for Antonio’s well-being and sympathizes with Shylock’s anger. It also drives a potential wedge between Bassanio and Portia so early in their romance.