Like System of a Down - but better!

Try him on Megadeth especialy the older stuff, that should be plenty of energy for him, still, you have to admit, SOAD are pretty creative, I have yet to se many bands like them.
 
You are obviously looking for catchy, sorta heavy songs that he can just groove to. I think Meshuggah, Intronaut, Mastodon, Genghis Tron are awesome bands but, might just be a little too much for the little guy right off the bat. Try Torche's Meanderthal album...very catchy, slightly heavy stuff but, quality.

He's 5....
 
^ Paysage d'Hiver s/t album. Fantastic ambient black metal if that's your thing. It's got insanely noisy production though.
 
Er....The Ramones? About as bouncy and "fun" as you can get and still acceptable to a 5 year old. Also some Pennywise would also probably strike his fancy.
 
System of a down are the epitome of terribly annoying shit garbage. Nothing on the radio has annoyed me even 2% to the extent they have. fuck I hate that band
 
how no one mentioned pantera ill never know

lamb of god and byzantine as well, and strapping young lad

ENEMY OF THE SUN!

their song emptiness is EXACTLY what youre looking for

so:

pantera:

art of shredding
shattered
primal concrete sledge
five minutes alone
hollow
slaugtered

LoG:

for your malice
vigil
laid to rest
again we rise
walk with me in hell (?)
grace
broken hands

strapping young lad:

love?
wrong side
almost again

Byzantine: (download the fundamanetal component and check out:

sin remover
my new casket
kill chain
filth of our underlings

enemy of the sun:

emptiness
feel the beating
lost in time