Answer:
I have a straight back and sharp teeth to cut objects.
I am a sound made by felines when petted.
Crooked as a rainbow and slick as a plate ten thousand horses can't pull me straight.
You can see it everyday, but cannot touch it at will. What is it?
I drift forever with the current and flows to your everyday life. I make living easy but I am good at killing people too.
I never sleep yet sometimes I weep. I can get angry or just be happy. Wherever you go, I will follow. No matter what you do, I will be there. I cannot die. What am I?