The ghost would influence Hamlet so as he reacts and kill his uncle by making him fight internally against his impulses caused by this tragedy and produced by his heart that is what he feels, and against what his use of reason says says that, eventhough his father his dead and he wants revenge, he knows that killing is a crime and he would have to deal with with the consecuences in case that he commits the crime. He would have to choose between follwing his feelings or his use of reason, and that is a real battle.
