It is difficult to define a method actor because this can mean so many different things. There is not a single “method” by which actors pursue this type of acting, and actors identified as “method” may have studied in diverse ways and under instructors who differ significantly in how acting should be pursued. The idea of method acting is not American in origin and comes instead from playwrights like Anton Chekhov and the Russian actor and director Constantin Stanislavski. Of the first generation of method acting instructors in the US, who began to coalesce in the 1930s, only Stella Adler was a student of Stanislavski, while others taught various forms of method by adapting from Stanislavski’s concepts.
The big movement of method acting really began to occur in the US in the mid 20th century, and then there were several instructors who taught different types of method. These include Lee Strasberg, Stella Adler and Sanford Meisner. A method actor could have studied with all or any of these teachers and may practice his or her craft via a variety of methods. Strasberg, for example, advocated many methods during his lifetime of teaching.
The Meisner method is often the one most closely understood as method acting by the general public. Meisner believed that the most authentic acting was reached when actors completely immersed themselves in their characters and acted in the moment to create a genuine response or action under imaginary circumstances. Though a performer's actions on stage may appear spontaneous, the Meisner method relies on heavy preparation beforehand, including exercises with partners and learning lines by rote.
The method acting advocated by Strasberg is more a sense of analysis of a character combined with using memories of the method actor to inform and fill a part. Stella Adler took this in a different direction and asked for even deeper character analysis. She is perhaps best known for the work of some of her students who include Robert DeNiro and Marlon Brando, both identified as strong method actors.
Essentially the job of the method actor is to determine how to inhabit the character and fill him or her with realism by using both analysis and sensitivity to the character and by drawing on emotions that are truly from life. There’s less judgment about the morality of the character and more a sense of how to bring that character to life in the most authentic way possible. It’s easy to think of “method acting” as employed by actors like Robert DeNiro or Brando. Either in the role of the Vito Corleone or the Godfather bring a fully realized character to the screen.
Another famous method actor is Dustin Hoffman, and actually, one of the best explorations of method for movie fans occurs in the film Tootsie. In the opening sequence Hoffman’s character is teaching other actors, and he continues to instruct actors through the film with Method principals, a hodgepodge of Meisner, Adler and Strasberg’s methods.
Other schools have since arisen that take some aspects of method acting to heart, but it would be unrealistic or unwise to say the only true actors are those who are method actors. Plenty of actors have nothing to do with any of the method styles and yet deliver performances that are chilling, emotional, or extraordinarily realistic. It can be said that the method actor has honed certain methods of the craft based most on perhaps Strasberg or Adler’s teachings, but there are many actors who are just as skilled and act by other and completely unrelated means.