Eisenstein - argued that montage was the essence of the cinema

Eisenstein was a pioneer in the use of montage, a specific use of film editing. He and his contemporary, Lev Kuleshov, two of the earliest film theorists, argued that montage was the essence of the cinema. His articles and books — particularly Film Form and The Film Sense — explain the significance of montage in detail.

His writings and films have continued to have a major impact on subsequent filmmakers. Eisenstein believed that editing could be used for more than just expounding a scene or moment, through a "linkage" of related images. Eisenstein felt the "collision" of shots could be used to manipulate the emotions of the audience and create film metaphors. He believed that an idea should be derived from the juxtaposition of two independent shots, bringing an element of collage into film. He developed what he called "methods of montage":

1.Metric
2.Rhythmic
3.Tonal
4.Overtonal
5.Intellectual

I also found this PDF document explaining further, but there are quite a few pages too look through, from what I read seems quite interesting.
http://cla.calpoly.edu/~dgillett/ENGL_411/pdf/DP_Chapter_2_selection_I.pdf

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