Considering that in the opening scene of Act 1, the witches warn us that appearances will be deceiving ("Fair is foul, and foul is fair"), there are many examples throughout the play of deceptive appearances and, consequently, their affect on relationships. As soon as Lady Macbeth reads in the letter that Macbeth sent to her about the Weird Sisters' predictions, she decides that Duncan must be killed to bring the prophecy to light. She tells her reluctant husband that they will kill the king and that he needs to put on the happy welcoming face of a good host as Duncan comes to their home in Act 1. sc. 7. Macbeth then says, "False face must hide what the false heart doth know." They have to pretend to be Duncan's loving subjects while they set up his murder. Later, in Act 2, sc. 3, Lady Macbeth upon the announcement by Macduff that Duncan has been murdered, pretends to faint in order to conceal her involvement in the murder. In Act 3, sc. 1, Macbeth uses his friendship with Banquo to ask him about his plans so that Macbeth can set up murderers to kill Banquo and Fleance. Again, deceiving appearances. Another major example of the effect of deceptive appearances is found in Act 4, sc. 1, when the Weird Sisters conjure up the apparitions for Macbeth to see. The apparitions make Macbeth feel invulnerable telling him that he won't be defeated by any man born of a woman or until Birnam Woods moves to Dunsinane. Act 5 reveals the tricks behind these words, but by then, it is too late for Macbeth. His desire for security has made him open to the deception.
The witches' anarchical formula couched in Chiasmus, 'Fair is foul, and foul is fair' initiates the theme of Appearance vs Reality quite early in 'Macbeth'. Macbeth is indeed so fair without and so foul within. In act1 sc.4, Duncan ironically foregrounds the same dichotomy when he says:
There's no art
To find the mind's construction in the face:
He was a gentleman on whom I built
An absolute trust.
Duncan trusted the thane of Cawdor who was 'a gentleman' by appearance, but he betrayed Duncan by siding with the king of Norway. Duncan proclaimed death sentence for Cawdor, and conferred the title on his most trusted general, Macbeth. Yet again, Duncan failed to see through the appearance of Macbeth's trustworthiness. Macbeth, 'chastised' by the 'valour' of Lady Macbeth's 'tongue', killed Duncan violating the virtues of 'kinship' and 'hospitality'.
Lady Macbeth chose to wear the appearance of cruelty to stand by the side of her husband's ambition. In reality she was not a virago. She suffered from a strong sense of guilt to become a victim of sleep-walking, and at last she killed herself. The dichotomy between Appearance and Reality vey severely affected her cojugal togetherness as well as happiness.
When Macduff went to England to convince Malcolm for a military venture against Macbeth, Malcolm suspected Macduff's bonafides. When as per Malcolm's instruction, his soldiers covered themselves with a branch , it appeared that the Birnam forest had been moving to Dunsinane. The appearance of the witches' equivocation came to reality.