What are Banquo's and Macbeth’s reactions to what the witches have told them?
From Act 1, Scene 3 of Macbeth
Concerning Shakespeare's Macbeth, you can read the basics of the two thane's reactions for yourself in Act 1.3. Most of what you need is readily apparent.
To clarify for you, I'll explain a detail or two and raise a point you may not notice upon a first or second reading.
The witches are androgynous, first of all. They appear to be women, yet wear beards. Macbeth and Banquo are, if anything, confused. Banquo is not afraid at all. He doesn't take the weird sisters seriously, and there's no evidence of his feeling any fear.
Macbeth, however, starts, or flinches, recoils, according to Banquo. This is significant. Banquo asks:
Good sir, why do you start and seem to fear
Things that do sound so fair?
Macbeth's flinch demonstrates his reaction to his being called the Thane of Cawdor and the prediction that he will be king. To flinch is to withdraw from as if from pain or anticipated pain, to tense the muscles involuntarily in anticipation of discomfort. Macbeth recoils, tenses up, withdraws.
Since we know that being named Cawdor and becoming king are not in themselves negatives to Macbeth, other reasons for his flinching must be present. A couple of possibilities exist.
First, the first genuine thoughts revealed by Macbeth, delivered when no one else hears, are located in his asides starting in line 130. In the second aside, Macbeth is already thinking of killing Duncan:
If good [the predictions, the witches], why do I yield to that suggestion
Whose horrid image doth unfix my hair,
And make my seated heart knock at my ribs
Against the use of nature? Present fears
Are less than horrible imaginings.
My thought, whose murder yet is but fantastical,
Shakes so my single state of man
That function is smothered in surmise,
And nothing is but what is not [nothing exists in the present but thoughts about the future].
First, then, Macbeth may flinch because he instantly recognizes what it will take for him to be king--killing the present king. And he fears doing that, as his later second thoughts reveal in Act 1.7.
Second, however, is the possibility that Macbeth, even before his encounter with the witches, has already been thinking of what it would take for him to be king. This would explain his instantaneous reaction to the predictions. He already knows what his becoming king would cost.
In short, Banquo does not take the witches seriously--not at first and not until the first prediction comes true (Macbeth is named Thane of Cawdor), and is never afraid of the witches. If he fears anything, he fears for Macbeth, that's why he warns Macbeth that evil agents sometimes give a small truth in order to mislead one into "deepest consequence" (128). Macbeth is not afraid of the witches, either. He is afraid of what will need to be done to make their predictions come true.
This particular scene from Macbeth is extremely significant as it places Macbeth at a crossroad in his fate, as well as introducing the theme of Ambition and Fair is Foul/Foul is Fair. And, although he recognizes that "nothing is/But what is not," Macbeth is tempted by the supernatural world.
In addition, the reader/viewer of the play is given insight into the characters of Macbeth and Banquo on this "so foul and fair a day" (1.3.39) While Banquo, acting as a foil to Macbeth, realizes the danger of dealing with the preternatural forces, he cautions Macbeth against believing the witches' statement that he will be king,
The instruments of darkness tell us truths,
Win us with honest trifles, to betray's
In deepest consequence (1.3.134-136)
However, Macbeth, in an aside, instead gives the prediction his consideration because, to him, "present fears are worse than horrible imaginings":
This supernatural soliciting
Cannot be ill, cannot be good...
But what is not....
If chance will have me King, why, chance may crown me,
Without my stir. (1.3.141-155)
It is at this point in the play that Macbeth, with his "vaulting ambitions," begins his path of entertaining the predictions of the witches as cause for his evil acts.
The first one to speak after the witches make their predictions to Macbeth is Banquo who asks, essentially, "What about me?!" They gave his friend such great news, he doesn't want to miss out on any good news for himself.
After the witches give Banquo his predictions, Macbeth tries to ask them to explain how what they said can be true? But, the witches disappear, leaving a bemused (puzzled) pair to wonder aloud if they had just been seeing things, or if they really had been visited by something supernatural. Then come these two lines:
I can just see them kind of elbowing one another and grinning at the prospects ahead of them. It's one of the last times things will ever be so carefree and friendly between them.
Macbeth is a story of greed and ambition and corruption; for this moment, though, these are two guys who have just heard some news which has made them a little giddy.