To embed a youtube video in a post, just copy and past everything in the youtube link after the equals sign ( " = " ). Then, put that in the youtube brackets.
As to the origins of the song you mention, I'll just go into the full details. That song is off of Dream Theater's third album "Awake" and it's about the former drummer Mike Portnoy's past alcohol abuse and him fighting against it.
Dream Theater are a progressive metal band, by the way.