Banquo is the first to notice the witches, questioning them and making observations about what the witches look like. Macbeth adds a one-line question: “Speak, if you can: what are you?” Already, Banquo seems more able or likely to question and challenge the strange beings, while Macbeth seems almost speechless.
After the witches hail Macbeth as thane of Glamis, thane of Cawdor, and “king herafter,” Macbeth stands startled and silent. We know about Macbeth’s amazement because Banquo says:
Good sir, why do you start; and seem to fear
Things that do sound so fair?
Banquo goes on to boldly ask the witches what they have to say about his future:
Speak then to me, who neither beg nor fear
Your favours nor your hate.
The witches reveal to Banquo that his descendants will be kings although he himself will not. Then the witches vanish as Macbeth finally speaks and tries to ask them more detail about what they mean with their prophecies about him. Macbeth wishes they had stayed to explain.
Banquo and Macbeth may be almost laughing the incident off except that Ross and Angus enter to deliver the news that King Duncan has awarded the Thane of Cawdor’s title to Macbeth as a reward for his courageous support of the King in the rebellion.
Banquo warns Macbeth that the witches--”the instruments of darkness"--could be winning them with attractive truths while in reality, the witches intend to betray them:
But ‘tis strange:
And oftentimes, to win us to our harm,
The instruments of darkness tell us truths,
Win us with honest trifles, to betray’s
In deepest consequence.
The first prophecy has come true. Because the witches hailed Macbeth first as Thane of Glamis, the title he already possesses, Macbeth says to himself; that “two truths are told.” If the first two are true, perhaps the prophecy about becoming king will be true, too.
Again, Macbeth seems more impressed by the witches and their prophecies than Banquo does. Does Macbeth have more ambition than Banquo? Has he already thought about becoming king? Macbeth thinks to himself that his hair seems to stand on end and his heart is pounding--he is already considering murdering Duncan:
My thought, whose murder yet is but fantastical...
In the meantime, Banquo stands with Ross and Angus; all three notice that Macbeth is lost in thought. Banquo is not a fascinated about the prophecies as Macbeth. Banquo even calls Macbeth back to reality:
Worthy Macbeth, we stay upon your leisure.
Macbeth comes to himself and gives the other men a lame excuse about why he was so distracted:
Give me your favour: my dull brain was wrought
With things forgotten.
Thus in this scene we see that Banquo seems more practical and cautious in considering the witches and their prophecies. Macbeth seems initially more startled and even speechless when he first sees and hears the witches. When he see that the witches have spoken some truth, he becomes fixated on the idea of being king--and even briefly considers murder to get kingship. Banquo is not so impressed with what the witches have said and even warns Macbeth to be careful.