RESEARCH - Purpose of Title Sequence and Film Opening

I learn that in a title sequence the characters need to be introduced throughout the movie. There is always background music/soundtrack to set the mood for the movie throughout the whole sequence.  There doesn't always have to be narration, but some movies require it when theres no music.  Little clips/images from the movie are usually in the sequence swell to give the audience some ideas of who will be in it and to help the audience familiarise themselves with the film beforehand.  The production company name distribution company will always be at the start of every film sequence.  Lastly, there is credits throughout the movie informing the audience of the directors, cast etc.

                 

                                                                Iron Man 3

                                                           

                                                              The Conjuring 

                                                             22 Jump Street