CONTEXT - SHAKESPEARE’S INTENTIONS
Warn the audience about regicide
James I was a very paranoid king, subsequent to his mother being murdered for attempted regicide against Queen Elizabeth. Since James was a patron for Shakespeare’s plays, the play Macbeth was constructed in order to warn the Jacobean audience about the detrimental consequences of regicide and how it leads to one becoming a carcass of their former self, therefore appeasing King James and settling his paranoia.
King Duncan in the play is constructed to be a sinless, innocent man as he is an avatar for King James himself.
Consequences of unchecked ambition
Shakespeare is warning the audience that excessive ambition will lead to a rapid demise, presented through both Macbeth and Lady Macbeth.
Betrayal of God’s will shall always be punished
Self explanatory.