Macbeth is Shakespeare's bloodiest play. Blood imagery dominates the action and the dialogue.
Before Macbeth takes the stage, he is described by the Bleeding Captain as being a ruthless warrior:
For brave Macbeth—well he deserves that name—
Disdaining fortune, with his brandish'd steel,
Which smoked with bloody execution,(20)
Like valor's minion carved out his passage
Till he faced the slave,
Which ne'er shook hands, nor bade farewell to him,
Till he unseam'd him from the nave to the chaps,
And fix'd his head upon our battlements.(25)
Later, Macbeth will kill Duncan (offstage) and the guards, and the Macbeths will have trouble washing their hands clean of the blood.
Still later, Macbeth will kill his best friend, Banquo, who will then haunt Macbeth as a bleeding ghost. Macbeth will have Macduff's family killed in a reign of blood, only to be revenged by Macduff, who beheads him.
All in all, blood is the language of the Thanes. They measure their success by it. "Blood will have blood," as Macbeth says.
So, blood is symbolic of the following:
- Worthiness as a Thane (the more blood shed, the more titles garnered)
- Unnatural cruelty and terror (murder of King, Thanes, women, and children)
- Guilt (being unable to wash it from one's hands)
- Cesarian birth (Macduff's bloody birth, not born of woman)
- Revenge (Macduff revenges his family's murders by beheading Macbeth)