Act I, scene 3 in Macbeth uses many literary devices, especially in the witches' dialogue.
"I will drain him dry as hay" (18)-- This line uses simile, comparing the dryness to that of hay. I like how the witch uses 'hay' in her comparison, something natural and common to the audience, which provides an interesting juxtaposition to the otherworldly strangeness of the sisters.
"So foul and fair a day I have not seen" (37)-- Macbeth uses alliteration with the repeating consonant sounds which make the words sound similar, but the actual meaning of the words creates a vivid contrast. This idea of contrast becomes a theme throughout Macbeth, that outward appearance does not always suggest inward motive.
"Into the air; and what seemed corporeal, melted, As breath into the wind" (81-82)-- Macbeth uses simile to compare the witches' disappearance to breathe evaporating in the wind. The comparison is an interesting one, because Macbeth and Banquo use the natural world (bubbles, water, breath) to explain an unnatural occurrence. This supports Shakespeare's developing theme of contrasting outer appearance with what is on the inside.
A literary device is a tool which, because it is used uniquely from writer to writer, promotes inventiveness and suspense. It allows writers to express themselves distinctively and to create extraordinary situations out of the most mundane or standard occurrences and also from the most heinous and hideous experiences. It also allows writers to introduce drama and intensity and to draw the audience or reader into the center of an event. Whereas in the twenty-first century we are often able to rely on visual effects to create drama to help us visualize what came before or is still to come, historically and in literature, that has to come from clever language use and manipulation.
Macbeth is dramatic in the extreme. Macbeth becomes a killing machine; Lady Macbeth goes insane, unable to wash out that "damned spot" (V.i.33); the witches relish their control over Macbeth who, even for them, represents "something wicked" (Iv.i.45); the woods at Dunsinaine "began to move" (V.v.34). These all represent the clever use of literary devices in creating the intensity of the situation.
In Act I, scene iii, Macbeth and Banquo, returning from a successful battle, meet the witches on this "foul and fair a day" (38). The audience has no doubt that the scene is quite desolate and dark and indicative of what may follow. Among the many examples of literary devices (including the foul and fair analogy) are simile, metaphor, hyperbole, alliteration; the list is endless. Shakespeare uses personification extensively in Macbeth, famously personifying sleep and, in the scene under discussion, the "insane root...takes the reason prisoner" (84-85). As Macbeth will abandon all reason and Lady Macbeth will go insane, using personification here and giving human characteristics to the insane root and to reason strengthens the conflicting circumstances of a day that is both foul and fair and it forewarns the audience that things are going to change.
Chance is also personified in Act I, scene iii and this is very significant because of Macbeth's reliance on the witches. The audience wonders whether Macbeth will allow time and circumstance to to take effect so that "Chance may crown me, Without my stir" (143).