* Matter has mass: Matter is anything that has mass and takes up space. Light does not have mass.

* Matter is composed of particles: Matter is made up of atoms and molecules. Light is made up of photons, which are packets of electromagnetic energy, not particles with mass.

* Matter interacts with gravity: Matter is affected by gravity. Light is not. It can be bent by gravity (gravitational lensing), but it's not attracted to massive objects in the same way matter is.

Light is a form of energy, not matter. It behaves differently and has different properties than matter.