There are currently 29 people in the world who are both the internationally recognized heads of sovereign nations and hold the title of king, queen or the equivalent. These rulers are called "monarchs."
There are hundreds of other individuals throughout the world who are considered to be part of subnational monarchies but are not necessarily recognized beyond their own areas of influence. These are locally accepted leaders of a community, state or tribe that are not associated with the government of the larger country in which they reside. Kings and queens such as these are common throughout Africa, where kings like King Goodwill Zwelithini KaBhekuzulu, current king of the Zulu Tribe, are recognized by others of their cultural group as being monarchs but lack any kind of authority or influence in government.