Macbeth, along with being the main character of a Shakespeare play, was King of Scotland from 1040 to 1057. There are many inconsistencies between the play and history. He didn't specifically murder King Duncan, instead he was killed in battle against Macbeth's army (most Scottish kings tended to have untimely deaths, either in battle or at the hands of their lords). Macbeth himself was killed in battle by Malcolm III's forces, assisted by an English army. No witches were involved.