Good Riddles

Question: I'll bring out your bulls,
and slow your roll.
I may even come out of your skull.

What am I?

Question: A container that takes no keys,
but a golden delight lies within me.

What am I?

Question: Paint me up to look real good,
Then take me to the shop to maintain under the hood.
Use a small brush to make no mistake,
Or just replace me with something fake.

What am I?

Question: It brings light to a dark dark world,
In a current it travels and through tunnels it's hurled.
Touch it and it'll kill you.

What is it?

Question: While you were folding a letter I got you.
Usually you will do whatever it takes to avoid me,
but now you can't help but find me.

What am I?