A motif is a recurring object or idea that regularly pops up throughout a text. When talking about a theme in a whole-text or extract-based question, it can help to link to motifs in order to tie your arguments together; for example, if you're looking at Romeo's feelings for Juliet in the play of the same name, you may discuss the biblical motifs that pop up whenever he discusses her.
Macbeth has many recurring motifs. Here are some:
1. Hallucinations
Macbeth himself hallucinates just before Duncan's murder ("is this a dagger I see before me?" Act 2, Scene 1) when he sees the dagger in the air - the first indicator of his descent into madness. This is later mirrored by Lady Macbeth, who sees blood on her hands that she can't get rid of ("out, damned spot!" Act 5, Scene 1). Both of these hallucinations occur before a major death. Funnily enough, Macbeth seems more cut up about Duncan than he does his own wife.
Macbeth also sees the ghost of Banquo at the dinner table (Act 3, Scene 4); this hallucination cements his decline into madness and emphasises the guilt he is feeling. Perhaps these images are linked to guilt, rather than death.
2. The Number Three
The number three pops up a lot in this play:
In my humble opinion, this is a reflection and subversion of the Holy Trinity. Macbeth focuses on the influence of withcraft and the supernatural on the ambitions of a young nobleman; of course he would want religion to be reflected here. The recurrence of this number isn't an accident!
3. Prophecies
The whole play depends on the prophecies that are made:
Most of these prophecies are answered in the course of the play. However, what remains unknown is whether these prophecies are only fulfilled because the characters knew about them, or whether the events of the play were fated and always meant to happen.
4. Violence
Macbeth is an extremely violent play, with many deaths:
Interestingly, most violence happens off stage and the audience never really get to see a person killed. Instead, we rely on the descriptions given by the characters.
It's also worth mentioning that the play both begins and ends with violence - a war.
5. War
Conflict pops up a lot in this story. We see Macbeth fighting with his wife, Banquo having doubts about his best friend and Macbeth arguing with himself over the decisions he has to make. In addition, the play both begins and ends with a major battle.
The idea of war and battle, both internal and external, is an important one. Macbeth doesn't work as a play unless you recognise the fragility of the main character and the mental conflict both he and his wife suffer with.