In The Merchant of Venice, the Prince of Morocco is the first of Portia's suitors to have to choose between the caskets of gold, silver, and lead to win her hand in marriage. He chooses gold because it is the most obvious choice, being the most valuable of the three substances.

The prince dismisses lead quickly as being entirely beneath both him and Portia. He pauses over the silver casket, on which is written "Who chooseth me shall get as much as he deserves." This is more tempting, since the prince is well aware of his advantages and thinks that he does deserve to marry Portia. However, when he sees the gold casket with its message "Who chooseth me shall gain what many men desire," he thinks this is even more apposite as well as more flattering to the lady.

Gold, the prince concludes, is the setting one would choose for the most beautiful and precious of jewels. It is ten times as valuable as silver. He also mentions that there is an English coin made of gold, upon which is stamped "the figure of an angel." All these considerations lead the prince to choose the casket of gold, but underlying them all is the simple and obvious consideration that gold is the most valuable substance on offer, and Portia, from any perspective, is a valuable prize.

The Prince of Morocco is given several options for the casket—lead, silver, and gold. He chooses the gold casket but it turns out that's not the right one. The inscription inside the gold casket tells the Prince of Morocco that he is bold but not wise, young but old-fashioned. He was not open-minded enough to think that Portia's picture may not be in the most valuable, most glittery and attractive casket. He is predictable in selecting the gold casket and he loses. He leaves empty-handed.

The next contender for Portia's hand selects the silver casket and he too fails. It's finally Bassanio who wins by selecting the lead casket. Bassanio wins because he makes his decision not based on outer appearance. He did not make the mistake of selecting the more valuable, better looking caskets. He did not judge based on appearance.

I think that this is a metaphor for a person who judges others based on their character and personality rather than their outer appearance. The one who forms an opinion of others based on their thoughts and actions is better than one who falls for outer beauty without a care for internal beauty.

Prince Morocco chooses the gold casket, and Act II, Scene VII is dedicated mostly to walking us through his reasons behind the choice.

The prince is trying to win Portia's hand in marriage. In order to do so, he must pass the test Portia's father has created for any of her potential suitors. As a suitor, he must choose from three caskets (decorative boxes) to try to find the one that holds a picture of Portia, which will be an indication that he has permission to marry her. Each box is made of different material; gold, silver, and lead. Each box also has an incription on it. For gold, the inscription reads, "Who chooseth me, shall gain what many men desire." On the silver casket, it says, "Who chooseth me, shall get as much as he deserves." The message on the final casket says, "Who chooseth me, must give and hazard all he hath."

Prince Morocco first decides to examine the lead casket closely. Upon reading the incription, he decides that the message is a warning to men who will risk a lot for worthless things, and he believes "A golden mind stoops not to shows of dross (line 20)." In other words, he doesn't choose the lead box because a man of worth won't bother gambling for something of such little value as lead.

Moving on to silver, he interprets the inscription to be a question of his own opinion of himself. He says he doesn't want to assume that everything he deserves includes Portia, However, he eventually concludes that if he says he doesn't deserve her he is only professing a low opinion of himself. He almost seems like he is going to choose the silver casket based on his feelings that he does, in fact, deserve Portia. "What if I strayed no further, but chose here (line 35)?" However, he decides to look over the gold casket before he makes his final decision.

It is here that Prince Morocco is most convinced by what he reads on the box. "Who chooseth me, shall gain what many men desire." This immediately makes up his mind about which casket to choose, because in his mind every man in the world desires Portia.

All the world desires her;/ From the four corners of the earth they come/ To kiss this shrine, this mortal breathing saint/...Is't like that lead contains her?/'Twere damnation/ To think so base a thought.../ Or shall I think in silver she's immur'd,/ Being ten times undervalued to tried gold?/ O sinful thought!Never so rich a gem/ Was set in worse than gold.

In the end, he chooses the gold casket because Portia is a highly desirable woman, so surely her picture would only ever be contained in a casket made of the most expensive, valuable material.