This film makes a very strange use of the Western genre. All the signs of a Western are there, but the mood is quite different from any other Western. Consider how this film differs from the conventional Western: in terms of its characters, its plot, its emotional dynamics, etc.
The film turns on the rivalry between two women, Vienna and Emma. How do you 'read' the florid, bravura performances by Crawford and McCambridge? What do you make of the way in which their performances are deliberately stylized, unrealistic, larger than life? What sexual tensions are expressed in and by their characters? How do these lead female characters relate to Johnny Guitar, Dancin' Kid, and the other male characters in the film?
In the context of the time when it was made, Johnny Guitar can also be regarded as a hidden political allegory, suggesting a liberal critique of McCarthyism: the mob is hounding innocent people for their supposed unsavory associations. Consider what is added to the film when it is seen in this context.