Macbeth is the main character in Macbeth, imagine that. Macbeth in the beginning of the play starts out as a very noble man.
But when he is confronted by Three Witches he starts down a long downward spiral that ultimintally ends in his death by the
hands of Macduff.

Banquo was a good man until the end. He too was told secrets of the future, but unlike Macbeth he did not strive to make them happen, instead Macbeth involuntarily did that for him. However Banquo was killed by Macbeth, because Macbeth feared Banquo's predicted future, which was that his sons will be king.

Duncan was king of Scotland until he was brutally murdered by his friend and servant Macbeth, just so Macbeth could become King. Duncan was a good man to Macbeth too, after the Thane of Cawdor was killed for his treasonous actions against the King, Duncan gave the title Thane of Cawdor to Macbeth, just as it was predicted by The Three Witches. Kind of ironic how the first Thane of Cawdor turned to the dark side, so Macbeth got it, and then turned to the dark side.

Macduff is the one predicted by The Three Witches to kill Macbeth. For he was not "born of woman" because he did not have a natural birth, so in turn he was able to kill Macbeth sense only a man not born of woman could harm him. Macduff had his suspicions of Macbeth when Macbeth became king so he fled to England and with General Siward planed an attack with the aid of the English King at the time to destroy Macbeth.

Lady Macbeth was the backbone of all the deeds that Macbeth committed to become king. At one point at the end of Act I
Macbeth was just going to let things be, but then after a long nagging speech by Lady Macbeth where she calls Macbeth a
coward for not trying to get what is promised to him (the crown). She then helps Macbeth carry out the deed, and much to her surprise she is haunted with images of blood on her hands showing her guilt, until finally she takes her own life.

Malcolm is the eldest son of King Duncan and also The Prince of Cumberland, which is the next in line to be King. After his
father is killed Malcolm flees for his life, which makes him look guilty of killing his father. He is out of the picture for awhile until Macduff also comes to England and they attack. After Macbeth is killed Malcolm returns to Scotland and becomes King. That is where the play ends, so we do not know when the prophecy of Banquo being the father of Kings actually does become true.

Siward was Earl of Northumberland, but more importantly general of the English forces. It is he that Macduff goes to for help.
Siward is the ultimate warrior, even when he learns that his son had been murdered the most important thing to him that he diedin battle, because he would not have it any other way. With his help Macbeth and his forces were defeated and Scotland was now free of his rule.

Even though there were actually three witches in all reality almost the same effect could have been done with just one witch.
The witches seem to be an evil, manipulating group of ugly old women. The play starts out with them talking of some evil things they have done, and then they begin to talk about Macbeth. When the meet Macbeth in Act I Scene III they tell Macbeth his future, or at least one variation of it, which eventually becomes reality because Macbeth wants it so much. So the cause of all of Macbeth's troubles could be traced back to these three "Weird Sisters".