Answer:
It flows out of the soil, It burns you if it boils, And holds us in its coils, More valuable than gold, As black as it is old.
It covers you, you lose it every day and you'd die without it.
Angels and pilots earn these.
It makes me warm and secure.
You fill it and it empties, A metaphor for plenty, Depending on what half you see, It's either full or empty