If you want to see a music video, there's a good chance you'll find it on YouTube. The downside is that YouTube doesn't offer any music-related feature, so you can't find information about the artists, lyrics or concert dates.
A simple Greasemonkey script adds one of these missing feature: lyrics. The script creates a container titled "Lyrics" below the video's description and shows the lyrics when you expand the container. Obviously, the video must contain the artist's name and the song's title. If the script doesn't find the lyrics of a song, change the site that provides lyrics or choose from one the alternatives.
As usually, to install this script you need Firefox and the Greasemonkey extension.