Standalone visuals almost never tell the full story of your video; the sound tells the audience how they should feel about the events on-screen. Music tracks are one of the quickest ways to inform the audience about a particular scene or shot. That wide panning shot over a woodland scene? A crawling, ominous death-march audio file instantly makes it sinister, while a light and upbeat music track will tell the audience there’s nothing to fear.
Music is an important layer for a video, and it’s important to follow copyright laws to make sure you’re using it lawfully and giving credit when necessary.