The most abundant substance on earth

It has more uses, and is described in more subjects then anything else on earth. At one time it was one of the seven words George carlin made famous. What is this substance?
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**** what else. There is mysterious ****, heavy ****. It comes packaged in a can, a box, and on it goes.
There is presidential ****, average ****, it never discriminates.

What type or usage can you think of?