Answer:
I move without wings, Between silken string, I leave as you find, My substance behind.
What do you throw out to use and take in when you're done?
I make you weak at the worst of all times. I keep you safe, I keep you fine. I make your hands sweat. And your heart grow cold. I visit the weak, but seldom the bold.
Two brothers we are, great burdens we bear. All day we are bitterly pressed. Yet this I will say, we are full all the day, and empty when go to rest.
You can always see it, but it's too far away to touch. Mountains rest on it, and at sea it surrounds you. What is it?
I am owned by Old McDonald.