The examples and perspective in this article may not represent a worldwide view of the subject. (March 2016)
In the federal Congress of the United States, the roles of the House Majority Leader and the Senate Majority Leader differ slightly. At the state level, the majority leader of a given state legislative chamber usually performs a similar role to that of their federal counterpart.
In the Senate, the Vice President of the United States is officially the President of the Senate and the President pro tempore serves as President of the Senate in the absence of the Vice President (or becomes President of the United States according to the Constitution). However, in reality, the Vice President seldom enters the Senate, let alone directly presides over the chamber, unless a tied vote is expected, and the President pro tempore has become a de facto ceremonial role deprived of any leadership ability.
Thus, the Majority Leader is seen as the de facto leader of the Senate, especially in modern times, and thus, in accordance with Senate rules, the Presiding Officer of the day gives the Majority Leader priority in obtaining recognition to speak on the floor of the Senate. In addition, the Majority Leader serves as the chief spokesperson for their party in the legislature (if the House is held by an opposition party) and the Senate.
In the House of Representatives the Majority Leader's presence and power often depends on the session. In some sessions, the Majority Leader takes precedence over the Speaker as House leader and legislative party leader either by force (which usually occurs when the Speaker of the House is unpopular) or because the Speaker of the House voluntarily surrenders power to the Majority Leader. In most sessions, the Speaker of the House takes precedence as house leader and party leader, with the Majority Leader being largely de facto irrelevant outside the fact they might be Speaker of the House one day.