Most witches we know are evil and wicked, so do the witches in Macbeth. They show up and tell Macbeth and Banquo a prophecy that relate to being the King, which is one of the reason that Macbeth killed Duncan, Banquo, and many others. When Macbeth is worried about Macduff and Malcolm are coming back to fight him, he goes to the witches and asked for help. Of course the witches “help” him by telling him to beware of Macduff, man born of women can hurt him, and as long as the forest didn’t move to his castle. But witches never tell the whole story, they only tell part of it, which gives Macbeth a false sense of security and finally meet his death.