In the recent past, humans considered the world around them to be composed of either mass or energy, energy being anything they could not put their hands around. Only within the past century has the notion that both mass and energy are solid particles become widely accepted.
Energy is just really small stuff, moving fast.
Increasingly, the really small stuff is identified, at least in theory as it is too small to be observed directly. The clues, for humans struggling to understand the world around them, lies in the behavior of small particles under different circumstances. Light is not composed of a singular particle, but dozens of particles, thereby accounting for much of what humans call the strange behavior of light. Rainbows are caused by the various particles responsible for what humans call color, the color of an object being determined by which particle is overwhelmingly present in the flood of particles striking the eye. Diffraction of light in water laden air following a rain storm results in what humans call a rainbow, where the eye perceives light particles sorted out by the degree, or angle, of diffraction from one side of the rainbow to the other.