In this scene, Lady Macbeth prepares herself for the impending murder of King Duncan. Her soliloquy and later dialogue with Macbeth is rich in meaning due to Shakespeare’s use of diverse literary devices. The soliloquy begins with personification:

The raven himself is hoarse
That croaks the fatal entrance of Duncan.

Like an announcer, the bird broadcasts a message and speaks until it is “hoarse.” An ominous symbol, the raven portends Duncan’s imminent death; its caw-like cry resembles the croaking noise made by a person on his deathbed.

Lady Macbeth then wishes to become a man in order to murder the king. She tells the spirits,

unsex me here,
And fill me from the crown to the toe top-full
Of direst cruelty.

Her command is rich with hyperbole or exaggeration. She wishes to be “unsexed,” or stripped of any signs of femininity. Then she can be an empty vessel ready to be filled from top (“crown”) to bottom (“toe”) until it overflows (“top-full”). The substance with which she would swell is the “direst,” or greatest, most extreme degree of cruelty, enabling her to commit murder without any hesitation. Later, she wishes for her murderous actions to be obscured by the “dunnest smoke of hell.”

Shakespeare uses alliteration to emphasizes the fluidity with which Lady Macbeth plans Duncan’s murder. She smoothly summons up courage and malevolence with alliterative words like “murd’ring ministers” (when commanding spirits to take and use her breasts’ milk for rancorous, not maternal, fuel) and “sightless substances” (when describing invisible evil spirits).

After Macbeth arrives, Lady Macbeth greets him with alliteration and hyperbole:

Great Glamis, worthy Cawdor,
Greater than both by the all-hail hereafter!

She tries to flatter and build her husband up with an exalted label like “Great Glamis” that flows easily and sounds grand to the ear. She elevates him above both titles (Glamis and Cawdor) and predicts an endless future (“hereafter!”) of greatness.

Shakespeare also employs synecdoche—when a part represents the whole—in Lady Macbeth’s speech. She uses her “breasts” to symbolize her womanhood. Later, she tells Macbeth to greet Duncan with false hospitality:

Bear welcome in your eye,
Your hand, your tongue.

Macbeth’s facial expression and demeanor (“eye”), physical actions (like a handshake, “hand”), and speech (“tongue”) all need to appear friendly and harmless in order to fool Duncan.

In her final speech, to Macbeth in this scene, Lady Macbeth advises him to hide his anxiety:

Your face, my thane, is as a book where men
May read strange matters.

Here, Shakespeare uses a metaphor to describe how expressive Macbeth’s expression is. On his face, others can “read,” or detect, what he is feeling and thinking—“strange matters” that would cause suspicion. As part of his wife’s strategy, Macbeth must look innocent in order to hide his murderous intent.

Lady Macbeth ends her speech with a final bit of pep talk. She tells him that if he follows her advice and leaves the dirty work to her, they will be rid of the obstacle (i.e., Duncan) blocking their path to future royal glory. The alliterative “solely sovereign sway” emphasizes the total and indisputable power that awaits them.

In this passage of the play, Lady Macbeth plots the murder of King Duncan, who is coming to her home to celebrate his victory in the war, and to honour Macbeth's role in that victory. Moments before hearing of Duncan's imminent arrival, she has learned that Macbeth has met with three witches, who have predicted that he will one day be king.

At the beginning of the passage Lady Macbeth delivers her first soliloquy. A soliloquy is a form of speech in which the character is speaking to him or herself, with no intended audience, and thus we can trust that the words they speak are a truthful reflection of their thoughts. The soliloquy begins with the image of the raven, which is a scavenger bird and often a symbol of death. Lady Macbeth references it here to imply that Duncan's death is imminent.

Lady Macbeth uses in her soliloquy lots of metaphorical language. She asks the spirits to "fill (her) from the crown to the toe top-full / Of direst cruelty" and to "make thick (her) blood." In other words she wants to be completely full of cruelty so that not even a trace of compassion remains. Blood is here a symbol for sensitivity and empathy, so Lady Macbeth is also asking, metaphorically, for her blood to thicken so that she will not be able to feel or empathize with the pain of others. She is preparing herself to be able to murder Duncan.

There is also in this soliloquy a recurring motif of darkness. Lady Macbeth asks the darkness to come ("Come, thick night") so that she can murder Duncan without herself or the heavens seeing what she is doing. Darkness also of course is a familiar symbol of evil and immorality, so when Lady Macbeth repeatedly calls upon it, the audience is able to infer that this is an evil, immoral character.

When Macbeth enters the scene, Lady Macbeth immediately tries to persuade him to help her murder Duncan, so that he can be king, and she can be queen. She tells Macbeth to "Look like the innocent flower, / But be the serpent under't." The first part of this instruction is a simile. She wants Macbeth to look innocent and harmless, like a flower, so that Duncan won't suspect the murder. In the second half of the instruction, Lady Macbeth tells Macbeth to, metaphorically, become a snake. A snake, ever since the biblical story of the garden of Eden, symbolizes evil and treachery, so Lady Macbeth is instructing her husband here to have (beneath the false appearance of innocence) murderous, evil intentions, like the snake.

Macbeth, of course, follows his wife's instructions, and as the play progresses, he becomes more and more like the snake. He lies, betrays friends and is treacherous, and by the end of the play is arguably a personification of the evil which his wife summons in this passage from act 1, scene 5.