Four? to the floor? You mean FALL to the floor, don't you? There's a song by that name.

It's nonsensical. "Four on the floor" can be used to describe either the bass beat heard in electronic music or the manual transmission in a car, and "petal to the metal" can describe aggressively pushing the accelerator of a car to drive fast. After taking a brief look at the lyrics, I think it's supposed to mean something like "full speed ahead", but it's not an expression anyone uses in real life.