Matter is defined, according to
General Relativity, as a massively condensed form of
energy. This property allows for the conversion of a tiny amount of matter into energy to provide power, both in a controlled electricity-generating form and a destructive uncontrolled form, as the citizens of
Hiroshima well know.
Matter also has the property, explained by
Albert Einstein, of
warping space around it. This
topographic manipulation is perceived by us as the
force of gravity. .
All known interactions in the
universe occur between matter and energy, or any combination of the two, and thus an understanding of both would basically constitute a
theory of everything. The closest thing, presently offered, to a
theory of everything is
superstring theory, which claims that the
fundamental particles we know of are actually only larger manifestations of
Plank-length sized
oscillating strings.