"To you, Antonio, / I owe the most, in money and in love" (1.1.4) Bassanio says to Antonio, his close friend. This friendship ties together the casket story and the bond story since Antonio asks Shylock for a loan on behalf of Bassanio who needs the money in order to court Portia. And, then, there is also the linking of the caskets with the loan from Shylock as an underlying motif that money is not, as Shylock the Jew feels, an end in itself, but is a means to help others in Christian charity by providing others that which they need. Because of his generous Christian nature Antonio extends himself dangerously, borrowing from the usurer Shylock and risking his own flesh for the happiness of his friend Bassanio.
In the end, then, the relationship between the caskets and the bond becomes more universal than the rivalries of Christian and Jew; this relationship furthers the important lesson of the lead casket that the attractiveness of gold is superficial, but the compassion that lies beneath the flesh, the compassion of the love of friends and parents is what is truly valuable.