Random Riddle: Together As One

We are often dangerous
But to some we are fun
To others we are frightening
Causing them to run
We come together
Though we seem apart
You see me and you hear my brother
Who oft times makes little ones run to their mothers,
I am bright and my brother is loud
And it may seem that we come from a cloud, What are we?
 
Random Riddle: Together As One