Poison Motif
Throughout the many murders in the movie, the motif of poisoning is obvious. King Hamlet is murdered by poisoning, although this is not widely known at the start of the film. However, it is revealed by the ghost of the victim, and Hamlet then decides to stage a play that portrays another similar poisoning just to see how his uncle reacts.
Claudius also tries to poison Hamlet, in two different ways. He first puts poison on the tip of the fencing foil that Laertes is going to be using in the duel. He also poisons the wine he will serve to Hamlet after the fencing match should something unforseen happen.
At the end of the movie, four characters die because they are poisoned, including Hamlet, the intended victim.
The Murder of Gonzaga Allegory
Hamlet asks the actors who are traveling with Rosencrantz and Guildenstern to perform a play called The Murder of Gonzaga in which a king is murdered when poison is poured into his ear. He intends this to be allegorical of his father's murder.
Talking to King Hamlet's Ghost Symbol
As he fights with Gertrude, Hamlet sees his father's ghost before him, and he begins to converse with him. Gertrude cannot see the ghost herself and so believes that Hamlet is either talking to himself, or talking to someone who is not actually there. She believes both of these are symbolic of his increasing madness.
King Hamlet's Ghost Symbol
The fact that his ghost is appearing to Hamlet is a symbol of the late King's inability to find peace in the afterlife because he knows that Claudius has not been held accountable for his murder. The appearance of his ghost is also symbolic of his need to avenge what was taken from him.
Claudius' Reaction to the Play Symbol
When Claudius reacts to the performance of the play The Murder of Gonzaga by leaping up from his seat and running out of the room, it is a symbol of his guilt in the murder of his brother. The play portrays an almost identical murder and a similar situation, and so the fact that he was hugely disquieted by seeing this symbolizes both his guilt and also the fact that he is now aware that Hamlet knows him to be guilty.
