Answer:
This is a shape and a symbol that we literally cannot live without. What is it?
It makes me warm and secure.
Securing your documents is easy with these trusty metal objects
A beautiful succession of sounds.
I am not alive, though I never die, to no one I've ever told a lie, today I can be god's warrior, and serve him with no horror, but tomorrow I might be devil's knight, for I am what ends the light.
All about, but cannot be seen, Can be captured, cannot be held, No throat, but can be heard. Who am I?