The first portion of act 3, scene 1 shows Banquo engaged in a soliloquy, a speech a character delivers when they are alone on stage:

Thou hast it now,—king, Cawdor, Glamis, all.
As the weird women promised; and, I fear,
Thou play'dst most foully for't: yet it was said
It should not stand in thy posterity;
But that myself should be the root and father
Of many kings. If there come truth from them,—
As upon me, Macbeth, their speeches shine,—
Why, by the verities on thee made good,
May they not be my oracles as well,
And set me up in hope? But, hush; no more.

A soliloquy tends to show a character's interior life, suggesting that the audience is being given access to a character's unspoken thoughts. This is a common device in Shakespeare's plays. On a stage, the audience needs the character to address them outright with this information, unlike in a novel or even a film, where the character's inner monologue can be portrayed as only existing in thoughts or voice-over.

Here, Banquo shares his thoughts about the fulfillment of the witches' prophecy in regard to Macbeth becoming king. Since it was prophesied that he himself would be an ancestor to kings, he shares his hope that the same will come to pass for his part of the prophecy. The soliloquy ends with Banquo noticing the arrival of other characters, so he halts his thought process (and therefore, the soliloquy itself) with "hush; no more."

Banquo's hopes are also a clear example of irony. Irony is when an event occurs contrary to what one would expect. Banquo hopes his part of the prophecy will also come true, not realizing that it is his murder at the hands of his former friend, Macbeth, that will make sure it comes to fruition.

Macbeth makes an allusion when he discusses his one-time friend, Banquo. He says,

There is none but heWhose being I do fear; and under himMy genius is rebuked, as it is saidMark Antony's was by Caesar. (3.1.59-62)

Macbeth compares himself to Mark Antony and Banquo to Caesar, implying that his fortune and fate will be less than Banquo's as a result of the prophecy which declared that Banquo would father a line of kings, whereas Macbeth would only be king himself. In this allusion, Macbeth compares himself to a famous and talented leader, someone legendary, and so this shows us not only his fear of Banquo's power but also his feelings about himself.

In this same speech, Macbeth describes his tenure as king as a "fruitless crown" (3.1.65). This is an example of metonymy: when something associated with a thing is substituted for the thing itself. The word fruitless signals Macbeth's lack of fertility, the fact that he will not father kings, that he is—in fact—not a father at all, and so he cannot pass on his crown to his line. The word crown signals Macbeth's role and status as king. He is very upset about...