Music helps. But, without structure the trailer is meaningless. A strong sound score can go a long way.
Since people here will want to makke a trailer for their indie productions. Remember, your cast, crew, characters, and story are unknown to the public. You need to introduce them.
Look up also spots for new TV series where a TV network is fact with a similar sinereo. They may use an actor in the cast as themselves to introduce the spot and ask viewers to tune in to see what the show is about. Then, they will show highlight scenes from the production to get viewers excited.
A weak sound score can kill both a trailer and the production itself. But, so can a lack of story and character structure.
The Underworld trailer is good because it introduces unknown characters and an unknown story. Solid production values, a tale of vampires and werewolves, and a good sound score helped to interest viewers to take a chance.