Figures of speech are tools that authors use to help readers, or in this case, audience members, identify with real world situations, objects, or senses in order to relate to the what the characters are experiencing. In the first act and scene of Shakespeare's The Merchant of Venice, there are many metaphors, idioms, similes and allusions to find. A few of the many figures of speech that can be found in the first act are shown below.
In the opening scene of the play, Antonio tells his friends that he is sad, but he can't figure out the reason why. Salerio provides his friend with a metaphor to show how his sadness forces him to suffer: "Your mind is tossing on the ocean" (I.i.8). Salerio then extends this metaphor for his friend, but also to let the audience know that Antonio has a lot riding on the ocean by way of merchant ships, literally. Since all of Antonio's money is invested on his ships currently at sea, he is probably more anxious about their success than he is sad.
Next, Solanio agrees with Salerio by saying that if he had so much invested on ships at sea, he would also be worried. To illustrate to Antonio what anxiety feels like to him, Solanio uses an idiom:
"I should be still
Plucking the grass to know where sits the wind
Peering in maps for ports and piers and roads,
And every object that might make me fear
Misfortune to my ventures out of doubt
Would make me sad" (I.i.17-22).
Salerio then uses a comparison between his breath cooling his soup and the winds at sea that might threaten his ships, if he had any:
"My wind cooling my broth
Would blow me to an ague when I thought
What harm a wind too great might do at sea" (I.i.22-24).
When Antonio tells his friends he isn't worried about his merchandise at sea, and that he really doesn't know why he is sad, Solanio says he just isn't happy. Then he uses a simile and an allusion to show that Antonio simply isn't laughing, which can make one sad:
"Some that will evermore peep through their eyes
And laugh like parrots at a bagpiper
And other such vinegar aspect
That they'll not show their teeth in a way of smile
Though Nestor swear the jest be laughable" (I.i.52-56).
Solanio explains that some people "laugh like parrots," while others may refuse to smile even if someone great like Nestor tells them a joke is funny. With this simile and allusion to Nestor (a great Greek hero from The Iliad) Solanio means to say that happiness can be a personality trait. Someone simply is or isn't happy sometimes and it is unexplainable.