Answer:
The answer is a human hair.
Explanation:
The human hair is inanimate, that is, not alive. Yet, it can stand up when we are, for instance, frightened. "Can start out copper" probably refers to the color. As we grow old and our hair turns gray, it ends up "as steel". A single hair is so fragile that a child can break it. However, lots and lots of hair are strong, resistant, to the point you can lift a man by pulling him by his hair.
