Shakespeare discusses love, marriage, friendship, and money in The Merchant of Venice through the play's three plots.
The first plot--the bond plot--focuses on friendship and money (two elements that should not mix according to Shakespeare). In the bond or contract plot, Bassanio who has squandered his wealth approaches his friend Antonio for funding for his quest for Portia's hand in marriage. Antonio acting as a loyal but somewhat foolish friend agrees without hesitation to loan Bassanio the money, but he does not actually have the money to do so at the time and must ask Shylock for a loan. The unwise contract that Antonio enters into with Shylock requires a pound of Antonio's flesh if he cannot pay back Shylock within the allotted time. At the conclusion of this plot in Act 4, Shakespeare portrays the strength of Antonio and Bassanio's friendship and issues a warning against entering into foolish monetary deals.
The second plot, the casket plot, involves Bassanio again and Portia. Through this plot, Shakespeare demonstrates his views on marriage and love. Portia, an independent woman, chooses to obey her dead father's wishes and allow the casket scenario to determine whom she will marry. By doing so, Portia gets to marry the person she would have chosen--Bassanio--and can rest in the knowledge that her future husband made a wise choice based on thought rather than appearance. This plot also allows Shakespeare to promote the idea that happiness ensues if children abide by their parents' wishes when it comes to marriage choices. Jessica's troubles result in part because of her deceiving her father.
The final plot, the ring plot, while not as strong as the other storylines does present love, friendship, and marriage. Portia and Nerissa must deal with marital issues when their husbands give up rings that they promised to keep forever. Portia proves her love for her husband by forgiving him and by settling the bond plot.