In this scene, Macbeth and Lady Macbeth are both feeling a great degree of doubt and misgiving about what they have done to attain the throne. Macbeth remembers that the witches’ prophecy did more than just say that Macbeth would one day be king, it also said that one of Banquo’s line would one day be king. This prophecy leads Macbeth to mistrust his old friend. Macbeth’s paranoia reaches its height as he hires murderers to kill Banquo.
The following lines from Act III, Scene II by Macbeth contain two literary devices:
We have scotch'd the snake, not kill'd it:
She'll close and be herself, whilst our poor
malice Remains in danger of her former tooth.
In this quotation, the “snake” is a metaphor that represents the dangers posed to Macbeth as king. The term “scotch’d” probably means “scorched,” and signifies that they have not completely eliminated the danger.
This is also personification, because Shakespeare is saying that the snake will take action like a human would.
In this scene, there are lots of examples of literary devices. First of all, Macbeth uses a metaphor to compare his enemies to a snake. He likens the act of killing King Duncan to slashing the snake. But because he has not yet killed Banquo, he tells Lady Macbeth that the snake is not dead. Moreover, he warns that they will be "threatened by its fangs" again if they do not kill it. In other words, Macbeth recognizes that if he does not kill Banquo and Fleance, his position as king will never be safe. (Remember that the witches prophesied that Banquo's sons would rule as kings of Scotland.)
In addition, Macbeth also uses personification at the end of this scene with the phrase, "Come, seeling night." In this instance, Macbeth gives the night human qualities and asks it to cover up the sun. Next, he urges the night to use its "bloody and invisible hand" to kill Banquo so that Macbeth may rule Scotland without fear of being removed.