Final answer:
The Vice President of the United States leads meetings in the Senate, while the President pro tempore fills in when they are absent.
Step-by-step explanation:
The President of the Senate, who is also the Vice President of the United States, leads meetings in the Senate. The President pro tempore, who is the second-highest-ranking official in the Senate and is typically the most senior member of the majority party, fills in when the Vice President is absent. The majority whip and the minority leader do not lead meetings in the Senate.
Learn more about Leadership roles in the U.S. Senate