Consider Einstein's equation:
E=mc^2, or m = E / c^2
This last equation suggests that matter (m) is nothing more than extremely concentrated energy (E), or to think of it another way, a tiny amount of matter converts to an enormous amount of energy.
Light, or at least the visible light we see, is defined as a narrow band of wavelengths in the electromagnetic spectrum. Consider your usage of the term "Light" to mean all of the electomagnetic radiation that could be found in all of the electromagnetic spectrum. Energy can be measured in terms of electromagnetic wavelengths, so light, as we've defined it, means nothing more than energy, and enough concentrated energy is nothing more than matter, so
Electromagnetic wavelengths = Light
Light = Energy
Energy = Matter
Light = Energy = Matter
The study of light and the interaction of light and matter is termed optics. The observation and study of optical phenomena such as rainbows offers many clues as to the nature of light as well as much enjoyment. Light is the kind of Mass-Energy that only moves fast or it does not exist. Matter is the kind of Mass-Energy that can exist standing still, and cannot ever go as fast as light. In the last century scientists figured out that matter can be turned into energy and back.‘We cannot quite build matter-things out of energy; so far it is too messy and we cannot control it. But it still means that matter and light-waves are sort of the same stuff, even though they move differently. Scientists call that stuff "Mass-Energy".
Light is energy. Energy is matter. Eienstien felt that energy and matter had a relationship