Even the witches of Macbeth seem disguised with beards, and Macbeth asks them what they are:
You should be women,
And yet your beards forbid me to interpret
That you are so. (1.3.47-48)
Certainly, they disguise their predictions with ambiguity, and Macbeth remarks that "nothing is/But what is not (1.3. 142) and wonders if he may not have to do anything to become king if "chance may crown me."
In Act IV, Scene 3 of Shakespeare's play, Malcolm tests Macduff's motives to be certain that he has not been sent by Macbeth by masking his true feelings. He confesses that he has many more vices than Macbeth and would make a poor king. When Macduff asserts that Malcolm is the rightful heir and that Macbeth must be defeated, Malcolm removes his mask and asserts that he is sincere and loves Scotland and was only testing Macduff:
Macduff this noble passion,
Child of integrity, hath from my soul
Wiped the black scruples, reconciled my thoughts
To thy good truth and honor....
...I here abjure
The taints and blames I laid upon myself, (4.3.129-139)
Moreover, Lady Macbeth and Macbeth himself are the greatest at masking themselves until they have worn the masks too long. As Nathaniel Hawthorne writes in his novel, The Scarlet Letter:
No man, for any considerable period can wear one face to the multitude, without finally getting bewildered as to which may be true.
Lady Macbeth has masked her own sex, her motives, and her guilt until she finally goes insane as she cannot remove the mask of bloody crime, seeing it always before her on the stairs. Macbeth has masked his ambition with dissemblance and blood, as well. He is driven by his "overleaping ambition" until he loses his belief in the witches' prophesy, which is itself masked, and he is undone by a man of integrity and nobility, Malcolm.
In Macbeth, Macbeth, Lady Macbeth, and Banquo must "wear masks" to hide how they feel in order to navigate among the other characters without having their inner feelings and thoughts detected. Lady Macbeth tells her husband that he must put on a "false face" in order to hide their plans to murder King Duncan. When Duncan and the others arrive at Macbeth's castle, Macbeth and Lady Macbeth accept the visitors with gracious welcoming even though they are planning the murder.
Banquo also wears a "mask" around Macbeth. When the two meet to discuss the witches' prophecy, Macbeth lies and says that he does not think of them. Banquo outwardly accepts Macbeth's claim; however, he believes that Macbeth has done ill deeds to get his new position of authority. Banquo must hide this from Macbeth because he fears the possible punishments that Macbeth might unleash.