Thanks for the puzzle.
The answer is - Gold.
Though desert men once called me God, today men call me mad. For I wag my tail when I am angry. And growl when I am glad. What am I ?
I know what my job is, The point has been made. You say I have a big head, And you're right, I'm afraid. Put me in my place, And then leave me alone. What I need most, Is someone to drive me home. What am I?
