Lady Macbeth is a very influential character in Macbeth’s life. She is the one who first suggests that Macbeth kill Duncan in order to become king. She is also the one who gives Macbeth the daggers to plant on Duncan’s guards, but she does not tell him exactly how to plant them or what to say when he plants them. Lady Macbeth is also responsible for smearing blood on the daggers and putting them back in place, as well as creating an alibi for Macbeth by telling the servants to leave the dinner table so that they cannot see or hear anything suspicious happening.
Lady Macbeth also helps create an atmosphere of fear around Macbeth by mocking him and telling him that he is not fit to be a king. She mocks him and tells him that he is not manly enough for such a high position of power. This influences his decision-making because now he feels like there is no way out of killing Duncan except by doing it himself (which makes sense considering his wife has already suggested it).