, the pathetic fallacy of the stormy weather reflecting the evil and good forces about to collide show straight away that the play is dramatic and grabs the attention of the audience. Shakespeare makes the Witches' intentions clear to us as soon as the Witches speak, that they're about to meet with Macbeth. We also see at the same time how evil they are; we hear about what the Witches have been doing to others and what revenge they'd like to take out on people who have angered them. For example, a sailor's wife offend one witch and the witch responds by drawing out a plan of attack on her husband: "Her husband's to Aleppo gone...I'll thither sail... I'll do, I'll do, and I'll do." (A. 1, S. 3, L. 10)
From this, we know what the Witches' mean to do. They are interested in the corruption of good people and it seems Macbeth is a prime candidate for their attention; at the beginning of the play Macbeth is seen as "brave", "valour's minion," and a "valiant cousin" (A. 1, S. ") until his utter corruption at the end of the play when he's seen as a "bloody butcher." The Witches mean to lead Macbeth astray and by prophesising what they do to him and Banquo they know they can goad his ego and ambition into actually carrying out acts to fill out the future they saw, acts which Macbeth wouldn't have had the guts to otherwise.
One thing that affects Macbeth greatly early on in the play is that one of the prophecies he hears from the Witches comes true, when he is greeted as the Thane Of Cawdor.
"I know I am Thane of Glamis, but how of Cawdor?" (A. 1, S. 3, Ls. 71/72)
Shortly after meeting the Witches he receives news of the betrayal of the King by the original Cawdor Thane and sees that he now has the title the Witches said he's one day own.
The other prediction of course has a big effect upon Macbeth &nd...