A viable and legitimate part of creativity is taking elements from the past or current media and making changes that reflect how you feel, how you perceive change or injecting humor in unexpected ways.
This involves using other people's content. There are ways to do this that respect the rights of copyright holders and permit a necessary free expression of commentary.
American University's Center for Social Media has a free guide to help you understand what you can and can't do when you want to uses copyrightable material in your video. There are many things to think about before you are tempted to plunk that song or clip in your video.