You will want to re-read the scene where these prophecies are given in Act I scene iii. Of course a chief debate in the play is about the nature of prophecies - if something is prophesied to happen, does that mean that we need to act to make it happen, or will it happen by itself? This is something that Macbeth himself ponders in his soliloquy in this scene. However, what is clear is that the news of this prophecy as its partial fulfilment (with the title of Thane of Cawdor being bestowed upon Macbeth) sets Macbeth and Lady Macbeth on a course of murder, crime and villainy. It is interesting that the murder of Duncan seems to necessitate other killings - blood leads to more blood, as Macbeth has to organise the death of Banquo and then goes on to slaughter Macduff's family.
The murder of Macduff's family inspires Malcolm to return with Macduff to fight against Macbeth. When his wife, children, and court are killed, Macduff is already on the way to see Malcolm in England. While he's there trying to persuade Malcolm to return, a messenger arrives bringing the news. After hearing of this tyranny, Malcolm agrees to bring the English army to Scotland to fight against Macbeth. The army's trick in the forest then is a major factor leading to Macbeth's downfall.
The prophecies of the witches encourage him to be aggressive in his actions to achieve the title of "King" more quickly than Fate would hand him that position. He is encouraged by his wife (equally ambitious) to murder Duncan. However, he alone decides to kill Banquo and Fleance in order to undermine the prophecy given to Banquo--he will not be King, but his sons will be.
Just to tackle one point you ask about, Macbeth goes to find the witches in Act 4.1 for more information and for reassurance. He seems to doubt the prophecies from time to time. Emotionally, he relies on them, but rationally, he seems to suspect that they are too good to be true, so he goes back to be reassured.
disucss the end of the play and how the final meeting with the sisters/macduffs family murder-leads to macduffs revenge and macbeths death
how have the witches tricked macbeth and the prophecies come true?
who is responsible for macbeths downfall?
Analyse Act 4 Scene 1. Why does Macbeth revisit the witches?
-look at the place/actions/weather/language of the women and how evil is created