Guess me : I ride forever with the current; down these long canals they’ve made; tame, yet wild, I run elusive........

Question

I ride 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 human life’s easy, I’m good at killing too.

Answer 1

An electron.