In Act III, Scene 6, Macbeth is described as a "tyrant"; it is explained that Macduff has gone to ally himself with Malcolm in England. What do these things tell readers about Macbeth's reign? What do they foreshadow about the rest of the play?

Basically thanes are fleeing Macbeth's castle. In act 5 sc 2 Angus notes of the people remaining, Those he commands move only in command, Nothing in love. The fact that most thanes have fled tells us that Macbeth's days are numbered. Macduff and Malcolm have gone to England to request King Edward's help. England, being perfect, often helps sort things out in Shakespearean tragedies. This foreshadows Macbeth's imminent demise.