I took my 6 year old to an Angels and Airwaves concert because we are big Blink fans and Angels fans. I took into consideration the venue, Moody Theatre in Austin, bought her hearing protection and we had some great seats in the balcony and it was not packed at all up there. We danced the night away and made some amazing memories.
It's all in the risk management and planning stages of doing something like this with kids. "What demographic would be at an Angels and Airwaves concert, what type of music is it, where are the seats.....etc"
I won't be taking her to a metal show until her teens but same concept there. And even so, I went to a metal show in NC and I moshed the night away. I fell down a time or two, just like everyone else, but as soon as you fall down, 2-3 people quickly scooped you up so you don't get hurt. Just the way things are done at that style of concert.