What is the purpose of a good opening sequence?

 An opening sequence generally deters what type of film it is going to be; immediately setting the tone, atmosphere and mood. It is used to give an insight as to the conventions that may be incorporated within the movie, will be, but also most importantly, in order to establish a storyline/narrative. Without these, audiences would be confused and have no idea of when, why or even what the film is about giving them the instant response to walk away. The industries of films need to maintain an almost persuasive opening sequence in order for the viewer to stick to what he/she is watching, and make it seem the duration of the film is similar to the quality as of the opening sequence. To entice the audience, micro aspects such as Mise-en-scene (setting, props, lighting etc.), cinematography, sound and editing need to used at a good enough standard so that the beginning seems very convincing; the movie is satisfying enough so that more people go to watch it, thus raising its views and enabling a potential sequel (depending on its popularity.)