In the UK the powers of the monarch under the British Constitution are not as comprehensive as they used to be.
This monarchy is a constitutional one, where the Queen herself is limited by her own country's constitution so she does not have very much power over her own government. The monarch mainly has three broad rights. Firstly, she has the right to be get consulted over important things. She should also hold the right to encourage, meeting with leaders and advisers, accepting resignations, dissolving governments and accepting new ones. She also has the right to warn, holding talks with government officials and putting things in perspective from a monarchy point of view. She has a royal prerogative over any new government.
Ever since the signing of the Magna Carta in 1215, the power of the British Monarchy has been transferred to Parliament, the legislative body. (The two Houses of Parliament are the House of Lords and the House of Commons.) This arrangement is called a "constitutional monarchy," (although even here the term 'monarchy' very relative.)
The 'Queen' or 'King' nevertheless has an important representative function, which should not be underestimated. For example, Queen Elizabeth formally opens and closes all sessions of Parliament, and she is often called upon to represent Britain in diplomatic ceremonies, both at home and abroad.
The Queen does indeed have some political sway in foreign affairs, but her power is limited. For example, her "vote" to have native populations in the Indian Ocean displaced (in order to accord an American military base a more strategic location) was vetoed in an international court.
In his essay "Brave New World Revisited," Aldous Huxley observes that for all practical purposes, the current constitutional monarchy in Britain is actually more democratic in function than Congress in the United States!
It is interesting to note the Britain, which bears the official name of United Kingdom of Great Britain and Northern Ireland, is not a single document, and much of it is not covered by any formally written document. The constitution has evolved partly out of laws passed by parliament, and partly from some old written documents such as Magna Carta. The constitution also incorporates common laws based on people’s customs and belief which are recognized by court of law. In addition to these documented parts of constitution, it also incorporates many unwritten important ideas and practices developed by people over the years – for example, the Cabinet system of government and the relationship between the Cabinet and the monarch.
The United Kingdom is a constitutional monarchy with the monarch accepted as head of the state, who reigns but does not govern. The country is governed by an elected government. The elected representatives govern the country through the mechanism of a Cabinet of officials called ministers.
The monarch formally declares open the Parliament, brings one session of Parliament to an end, and dissolves it existing Parliament to an end. The monarch also formally passes an act passed by parliament by giving the royal assent. Though there is no written down rules, by tradition, the monarch acts as per advice of ministers.