Best instance of this I have seen; a young band belting out one of their own numbers. The rhythm guitarist was leaning back, eyes closed and smiling beatifically as he thrashed away. Alas, one of the other musicians had accidentally pulled the lead out of his amp. All the gorgeous noise was coming from the lead guitarist, John "Fingers" ****, who was playing with all the expression of a man ironing a shirt.

By all means, get into the music, but do pay attention to what is going on around you. Otherwise, you miss vital chord changes, quiet sections to let the vocalists be heard, flying vegetables ...