Symbols are objects, characters, figures, and colors used to represent abstract ideas or concepts.
Blood is everywhere in Macbeth, beginning with the opening battle between the Scots and the Norwegian invaders, which is described in harrowing terms by the wounded captain in Act 1, scene 2. Once Macbeth and Lady Macbeth embark upon their murderous journey, blood comes to symbolize their guilt, and they begin to feel that their crimes have stained them in a way that cannot be washed clean. “Will all great Neptune’s ocean wash this blood / Clean from my hand?” Macbeth cries after he has killed Duncan, even as his wife scolds him and says that a little water will do the job (2.2.58–59). Later, though, she comes to share his horrified sense of being stained: “Out, damned spot; out, I say . . . who would have thought the old man to have had so much blood in him?” she asks as she wanders through the halls of their castle near the close of the play (5.1.30–34). Blood symbolizes the guilt that sits like a permanent stain on the consciences of both Macbeth and Lady Macbeth, one that hounds them to their graves.
As in other Shakespearean tragedies, Macbeth’s grotesque murder spree is accompanied by a number of unnatural occurrences in the natural realm. From the thunder and lightning that accompany the witches’ appearances to the terrible storms that rage on the night of Duncan’s murder, these violations of the natural order reflect corruption in the moral and political orders.