According to a University of Chicago glossary, in the early history of film, the Soviets sometimes used montage to make ideological statements about issues such as government cruelty. They also used montage to give viewers a sense of fragmentation or disharmony.
In American films, montage has more often been used not to advance an ideology but to help narrate a story, showing what happened in different times and places.
Montage can be used to build suspense. For instance, director Alfred Hitchcock used montage in the well-known shower scene from "Psycho," cutting quickly from images of the slashing knife to images of Janet Leigh screaming in the shower, and telling the story of the murder without showing it directly.
Filmmakers sometimes use montage sequences to express the passage of time. For example, a filmmaker might use montage to reveal what a teenager did when her parents left the house for an hour.
In moving from one image to another in montages, filmmakers often use dissolves or multiple exposures.