Final answer:
The Vice President of the United States leads Senate meetings as President of the Senate but only votes to break ties. The President pro tempore presides in their absence and is a ceremonial role, with majority and minority leaders holding actual power.
Step-by-step explanation:
The individual who leads the Senate meetings is the Vice President of the United States, who holds the official title of President of the Senate. However, the Vice President typically votes only to break ties. In the Vice President's absence, the Senate meetings are presided over by the President pro tempore, who is usually the most senior senator of the majority party. The President pro tempore is selected by the Senate members and holds a largely ceremonial role, as the real power is exercised by the Senate's majority and minority leaders who manage the legislative flow and negotiations.