The play Macbeth is written with much inlaid imagery of light and darkness. Each act of the play has contrasting images in the battle of the light vs. darkness. The light and darkness are actually metaphors for the fight of good vs. evil. All the scenes with light are the scenes that do no involve Macbeth's corrupt nature or ones that show the people who are good and will fight for good, like in England with Edward. The scenes with darkness are the ones where the Great Chain of Being is shown to be breaking, and of course the ones with the murders of Duncan and Banquo. Shakespeare uses the light vs. darkness to show the contrast of power in the play and to show where evil is hidden in different acts.
In the first act, the play opens with thunder and lightning, and the description is of a dark night. This sets the play with an eerie feeling, perhaps one of danger. The bad weather is then followed by the arrival witches, who with their "Fair is foul, and foul is fair," chant get the play off to a foreboding start. We learn that Scotland is in the middle of putting down a civil insurrection and the Norman forces, certainly a dark state of affairs. In the rest of the act, darkness overshadows the light as Macbeth plots to kill Duncan, the good and kindly king. In I, IV, 57-58, Macbeth asks that "Stars, hide your fires/ let not light see my black and deep desires." Macbeth does not want the light (goodness) or the goodness in his own heart to see that he is willing to murder Duncan to get the crown. Lady Macbeth also implores in I, V, 57-60, "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." Lady Macbeth doesn't want to see what she is going to do, and naturally she doesn't want anyone else to see either. The "blanket" of dark will cover her as she takes care of the deed.