Macbeth receives four prophecies from the witches, all but one make Macbeth feel invincible.
The first prophecy tells Macbeth to "Beware the thane of Fife" (IV. i. 72), who is Macduff. This Macbeth already knows, but since the prophecy is true, Macbeth will firmly believe the next three, which will set up Macbeth's demise.
The second prophecy tells Macbeth
"Be bloody, bold and resolute. Laugh to scorn
The power of man, for none of woman born
Shall harm Macbeth" (IV. i. 79-81).
Essentially the message tells Macbeth that no man can harm Macbeth; thus his image of himself grows enormously; he is feeling invincible, for thus far the witches have not lied to him.
The third prophecy tells Macbeth to
"Be lion-mettled, proud,and take no care
Who chafes, who frets, or where conspirers are.
Macbeth shall never vanquished be until
Great Birnam Wood to high Dunsinane Hill
Shall come against him" (IV. i. 90-95).
These lines strengthen Macbeth's false sense of invincibility for what they state is that he will remain king until the forest, Brinam, uproots itself and attacks his castle; Macbeth knows this is impossible, and therefore, feels invincible.
But the last prophecy unnerves him, for in it he sees Banquo's lengthy legacy of sons who will be kings; remember, that in Act III Fleance is able to escape the assassination plotted by Macbeth, and remember what the witches tell Banquo in Act I that "thou shalt get kings, though thou be none." And remember that Macbeth is there, so everything the witches have stated has come to fruition; thus Macbeth believes in what the witches have told him, which in Act IV not only make him feel invincible, but set him up for his demise, for all three prophecies come true.
- Burinam Wood seemingly uproots itself and attacks Dunsaine Hill by way of the English forces cutting down branches and holding them in front of themselves to conceal their numbers.
- Macduff does slay Macbeth only because he was born by way of a Cesarean section, which during this century was believed to be unnatural , and therefore, Macduff was not considered to be a man born of woman.
The messages/prophecies most certainly make Macbeth feel like some sort of god, and thereby make him feel invincible, and his invincible image of himself is what actually brings him to his demise, for instead of fleeing for his life, he remains and faces the English forces and Macduff.