Answer:
It is the great nemesis of the lactose intolerant.
Salty water everywhere but not sea in sight.
I am the tool, for inspiring many. Buy me in the store, for not much more than a penny. Don't overuse me, or my usefulness will go.
Iron roof, glass walls, burns and burns and never falls.
It regulates our daily movements, but it feels no interest in our lives. It directs us when to come and go, but does not care if we pay attention. What is it?
I am owned by Old McDonald.