The president of the United States is one of the most powerful leaders in the world. He or she can often change the course of history. In part, this is because the president serves in many roles. These include head of the government and commander in chief of the armed forces. The president is also the leader of his or her political party.

The president is the ceremonial head of the state (meaning "country"). He or she meets with representatives of other governments. There are also many ceremonial duties. For example, the president holds state dinners and give medals of bravery to soldiers.

Some of the president's jobs as head of state occur in the White House and Washington, D.C. Others take place in other parts of the country. So the president travels often. In addition, presidents travel extensively to foreign countries. As head of state, the president symbolizes the authority and power of the United States. So he or she acts in the name of all Americans.

The president is also the head of the government. In this role he or she is also the chief executive, chief diplomat, commander in chief, and chief maker of policy.

As chief executive, the president appoints the heads of the government departments. (These department heads make up the president’s cabinet.) The president also supervises the work of the government’s executive branch. This by itself is an enormous job. So the president frequently finds it hard to stay informed about everything that is happening. For that reason he or she relies on the staff of the Executive Office. This staff includes many clerks and assistants. Examples include the chief of staff and the press secretary.

With their help, the president provides leadership in many areas. One is legislation (creating laws). The president sets the lawmaking agenda for Congress. Sometimes he or she proposes new laws. And Congress debates and passes (or rejects) them. In addition, the president delivers a long speech to the nation each January. This is the State of the Union address. It outlines what is happening in the country. The speech also points out existing national problems and suggests ways of solving them. Soon afterward, the executive branch issues an economic report. It also issues a detailed budget. The budget lists the president’s programs and objectives for the near future. And it estimates what they will cost.

The president can also check, or limit, Congress’s activities. One way this is done is by trying to restrict congressional spending. The president can also meet with leading members of Congress. He or she can try to convince them to pursue or not pursue a certain policy or program. Another method the president can use to check Congress's activities is the veto. A veto is a presidential rejection of a proposed law. Some presidents have used vetoes fairly often. In 1975, President Gerald Ford vetoed 18 bills. In contrast, Presidents John Adams and Thomas Jefferson never vetoed a single bill. The mere threat to veto can be powerful. It can sometimes allow the president to shape legislation to his liking.

The president is the nation's chief diplomat. He or she deals directly with the heads of foreign governments. One example is meetings with leaders of the Group of Eight (G-8) major industrialized nations. These occur regularly. In addition, presidents oversee negotiation of major treaties with other countries. An example was the Panama Canal Treaty of 1977–78.

As commander in chief, the president is in charge of all national military forces. He or she can send troops overseas. The president can also order them into combat. Usually this is done to protect the interests and lives of U.S. citizens. Some presidents have also used the military inside the United States to maintain the peace. In extreme situations, a president can impose martial law. (Martial law is rule by military force.) President Abraham Lincoln did so during the Civil War. Additionally, the president is the only person with the authority to order the use of nuclear weapons.

Civilian control of the military is important. A dramatic example of this principle occurred in 1951. President Harry Truman fired the famous army general Douglas MacArthur. (MacArthur had openly criticized the commander-in-chief’s policy during the Korean War.)

As chief policy maker, the president creates guiding principles for issues that concern Americans. For example, the president decides what he wants to accomplish in areas such as education, crime, and unemployment. President Lyndon Johnson established his Great Society program. This included programs for health care for the poor and pollution control. Johnson also encouraged the civil rights movement. On the other hand, President Ronald Reagan cut funding for social programs. He felt they were too expensive.

The presidency is the top position in American politics. So the president is usually the country’s main political leader. He or she is also the leader of his or her political party. The president chooses the chairperson of the party's national committee. And the president tries to maintain the support of state and local party organizations. This can help get Congress to enact the president's programs.

As head of the party, the president is expected to campaign for the party in various elections. He or she also appears at party fund-raising functions. The president also tries to build alliances among supporters. These include ethnic and racial groups and business and labor leaders. Such groups are needed to help the party win national elections. Additionally, the president manages patronage for his party. That is, the president rewards supporters with jobs. These jobs can include being a cabinet officer, a judge, or an ambassador to a foreign country.

The better a president is at leadership, the more successful he or she will be in office. The personalities of presidents play a large part in their success. Presidents must be confident, skilled communicators. And they must be personally appealing to fellow politicians and the public.

The president has always been a major symbol of the nation. He gives voice to its hopes and fears. The president has become a major source of media attention. The media follow him or her everywhere. The president's every personal appearance, word, or movement can become news.