Riddles ♣ 25-06-2013

I drift forever with the current
down these long canals they've made
Tame, yet wild, I run elusive
Multitasking to your aid.
Before I came, the world was darker
Colder, sometimes, rougher, true
But though I might make living easy,
I'm good at killing people to0 !!! 

Who am I ? 

Answer : Electricity