By analyzing great trailers, I have found a pattern throughout their composition and how they are organized - a sort of common theme or formula if you will.
Great trailers typically begin with an intriguing sound such as something epic; for example, the first thing you may hear on the trailer is the sound of sirens or gunfire or suspenseful music being played as the studio's name appears. Then the pattern begins.
The main character's virtues or abilities are highlighted.
The main predicament or challenge of the story is explained in terms of the rest of the casts' voices (or a narrator) with related shots.
A flurry of action shots (or emotional reactions in case of 'chick flix') follow as if they are the answer to this predicament, but without giving away the details of the plot.
The trailer ends with a final clincher comment or one-liner.
The music also typically follows this same type of pattern as its job is to describe whatever is being seen. Then towards the end when the final flurry of action shots roll, we hear the music climax and stop before concluding with a long tonic bass line as the one-liner is stated over this sound or final narrative comment.
A similar pattern exists for creating the synopsis of great movies. For example, as you are sorting through movies to watch at a typical online streaming service, you will find that most synopsis that you read are an average of around two lines. Some get it down to one sentence.
In that sentence or two, you are told 1) what the predicament is and 2) who the antagonist is (if applicable), as well as 3) who the protagonist is and 4) what they're doing to resolve the challenge. For example, here are some generic examples for you to study.
An elite group of anonymous bad guys are chased by a federal law officer who uncovers a much deeper, darker conspiracy behind the bad guys' routine crime wave.
A really, really bad guy escapes federal custody during transit, and the good guy tracks him down just in time to stop him from obliterating the planet.
The world's most lethal operative is drawn out of hiding by a tragic event to learn who the unknown terror group is behind this event.
A group of people with special talents pursue a unique challenge perpetrated by a group of unknown rich politicians with hidden agendas - a challenge that could cause massive chaos
An average person is selected by a random accident to solve a crisis because nobody else is available to stop this incoming disaster.
A child is recruited by intelligence for his unique abilities to stop certain covert bad guys in this action-packed thriller.
When a group of crazy super bad guys steal a military tech instrument of mass destruction that poses a global threat, the world needs a super good guy to save the world in this adrenalin-pumping action movie.
This is the tale of an elite good guy team who make final stand to save the world from earth's most dangerous crazies.
When Joe the Innocent is framed for treason, Mr. Awesome discovers it is due to a massive government conspiracy. Mr. Awesome risks all and pulls out all of his most clever tools of the trade to uncover the dirty secrets and bring the world's most powerful organization who will stop at nothing to end Mr. Awesome's courageous attempts.
A great movie typically is based upon a great theme, and usually that theme involves human emotions such as fear or triumph, and the challenge faced is usually something that the majority of audience members also find very important such as a terror attack, a world-wide peril, or a person of importance being killed.
Great movies often share similar basic characteristics in other aspects as well, but this is the typical pattern I have found in relation to movie trailers and their synopsis.