Both Shakespeare's Macbeth and Orwell's 1984 examine the idea of power: how it is gained and how it is maintained.
Macbeth gained his power through bloody violence—the killing of King Duncan makes his rise to the throne possible. He then maintains power through the continued use of violence—the killing of Banquo and then Macduff's family.
In Orwell's 1984 power is gained and exercised in a more subtle way—through the use of surveillance technology. Macbeth didn't have access to advanced devices like cameras and microphones, although he did have spies.
In both cases the citizens are tyrannized, and the effect is to frighten people into following authority even when it is not in their own best interest to do so. The difference is that we see Macbeth's power come to an end whereas in 1984 the government is not defeated.