In "Macbeth" there are two themes that are central to the play and another motif that is also prevalent: (1) Ambition and its psychological burdens , (2) Unnatural world vs. reality, and (3) Love
"Ambition should be made of stronger stuff" Marc Antony remarks in his funeral oration of Caesar, and this proves to be a problem for Macbeth as well as Lady Macbeth, who in their ambitious desires commit evil deeds and embrace evil in order to attain power. Accepting the prophecy of the witches unconditionally, Macbeth murders Duncan. But, as Frost writes, "way leads unto way," and Macbeth commences his guilt-ridden pathology of evil, which generates more evil deeds, and eventually madness. So, he murders Banquo and fearing the prophecies of the witches, he steeps himself in cruelty and evil as he murders the family of MacDuff.
The unnatural world whose prophecies dictate Macbeth's evil doings clearly overturns reality for him as well as for Lady Macbeth who, in her ambitions for her husband, transforms herslef into an unnatural, desexualized evil spirit. However, Lady Macbeth is no match for the witches and she enters a realm of insomnia and madness from which some critics say she only returns when she becomes rehumanized by her suicide.
This unnatural world of evil which causes Lady Macbeth's madness also leads to the illusions of Macbeth--is this a dagger I see?"-- and his paranoid delusions-Banquo's ghost, the tricks of the witchcraft--he cannot be harmed by anyone "born of woman"-- which lead him to believe MacDuff's family must be killed.
Yet, ironically, Macbeth and Lady Macbeth have a strong love relationship. One of Lady Macbeth's final thoughts is solicitous of her husband; upon her death, he grieves greatly and ponders the brevity of llife and his weariness with life now that his wife is dead in the famous passage "Out! Out! brief candle."