The first recurrent image is the dark or darkness. Dark represents evil and hell. All of our fears rise in the dark. We can see that most of the mains scenes happen in a dark place or during the night. In fact, all the murders and treasons are done in darkness as if the dark could cover and hide the horrible deeds.
For example, in act I scene V l. 53 to 56, Lady Macbeth says: “Come thick night, And pall thee in the dunnest smoke of hell, that my keen knife see not the wound it makes, Nor heaven peep through the blanket of the dark, To cry, Hold! Hold!”
In this passage, Lady Macbeth is thinking about Duncan’s murder, and she wants to act in darkness so she will not see the murder. In that way darkness blinds out all of the terrible things that could be done.
Then, the scene of Macbeth’s vision of the dagger happens in the complete darkness so the vision of his future murder comes to Macbeth only at night when no light can bring him back to goodness.
Banquo’s murder also happens in the dark. Such evil deeds could only be done in the dark.
Then during Lady Macbeth’s sleep walking, the only source of light comes from the candle that she keeps by her at night. In fact, Lady Macbeth is very afraid of darkness because it makes her remember of all the deeds that happened during the night. (Here, light has a positive reassuring role.) In this scene, she reveals all the crimes that her husband committed with her support.
In conclusion, darkness intensifies the horrible deeds and murders and brings a very fearful ambiance to the play.
The second image is the one of the sleep that is kind of related to the one of the dark because dark and sleep comes together.
Firstly, we can see that Duncan is killed during his sleep. This fact is even mentioned by Lady Macbeth in act II scene 2 l. 15 to 16: “Had he not resembled My father as he slept, I had done’t.”
Then, in the same scene, Macbeth says l. 46 to 47: “Sleep no more! Macbeth does murder sleep!”