Tragedy
The film itself is a tragedy, but it has tragedy as one of its central themes as well. After all, there are no happy endings in this narrative. Everyone dies, either at their own hand because they are made irredeemably miserable, or at the hands of someone else who wants to murder them to get them out of the way. The royal family of Denmark is no more, largely because of the actions of one man, Claudius, that start the dominoes falling until every member of Hamlet's circle is dead.
The initial murder, that of King Hamlet, is avenged, which is a positive thing, but in this occurs the deaths of four other people. These deaths are all tragedies in of themselves.
Murder
The plot centers around a murder, although it has already been committed by the time we actually meet any of the characters. Claudius has murdered his brother to gain control of Denmark for himself. In order to cover this up, and prevent Hamlet from revealing the truth, the then plots a series of events that will enable him to murder Hamlet. At first he tries to offload this task onto the King of England by way of requesting an execution, but when Hamlet manages to turn the tables on him, he is then forced to come up with a second plan. He is a gifted poisoner, having murdered his brother by poisoning him, and so puts poison in the tip of the fencing foil that Laertes is going to use in their hand-to-hand duel. He also poisons the victory wine as a back-up plan just in case Laertes should lose the duel. This ends up poisoning his wife.
Hamlet murders Polonius which is also indirectly Claudius' fault, because Hamlet believed it was he who was trying to restrain him, rather than Polonius.
Maniupulation and Scheming
All of the characters in the movie are manipulative and they are all intent upon making alliances that will enable them to meet their goals. The only character that proves himself truly loyal and steadfast is Horatio whose friendship to Hamlet never wavers. Each of the characters, including Hamlet, creates an elaborate succession of plans that will create the impression of one thing whilst something else entirely is going on; for example, Hamlet decides that he will give the impression of madness.
Contemporary Political Issues
When Shakespeare wrote Hamlet, there was significant kingdom-building going on in Europe and this theme shows itself at varying intervals in the movie as Denmark and Norway vie for expansion. Although the King of Norway is not intending to take over Denmark, and opts instead to invade Poland with a view to expansion there, he finds the royal family dead when he arrives at the castle, and realizes that he is able to expand his kingdom without having to fight or engage in any kind of battle whatsoever.
