Usually, but not always, public art is commissioned specifically for the site in which it is situated. Monuments, memorials, and civic statues and sculptures are the most established forms of public art, but public art can also be transitory, in the form of performances, dance, theatre, poetry, graffiti, posters and installations.

Public art can often be used as a political tool, like the propaganda posters and statues of the Soviet Union or the murals painted by the Ulster Unionists or the Irish Republicans in Northern Ireland. Public art can also be a form of civic protest, as in the graffiti sprayed on the side of the New York subway in the 1980s.