If you choose to use music in your video, you can't just download a popular song from the internet. Artists earn a living by licensing music for use in film, TV, and other videos. You will need to find music that is ROYALTY-FREE and LICENSED FOR FREE PUBLIC USE.

Tracks are often made available under a CREATIVE COMMONS license. Don't forget to credit your source - most licenses will require it, and attributing a work to the author is a requirement for school projects. Visit the Creative Commons website for more information.

A good place to find music for your project is Silverman Sound. This site has a nice tagging feature, descriptions of each track, and clear instructions on how to credit the source in your project.