"Unlicensed" is the red flag here. You have no rights to copy the song. You as the editor are responsible for purchasing a license to use the song. Unfortunately, the license for a popular song would be in the thousands and there has not been any solution for small businesses who just produce wedding and birthday videos. So, no it is not legal. Will you be sued? If your business becomes worthy of suing, then yes, you can and will be sued.
Commercial purpose is not the same as publishing. If you are being paid to create something with someone else's copyrighted material, you are infringing copyrights. If you are creating it for fun, no payment, and not publishing it then you are probably protected under fair use.
Disclaimer:This is all for educational purposes only.