Solid light is a hypothetical material, made of light in a solidified state. Theoretically, it is possible to make such a material, and there are claims this material was already made, including claims from MIT and Harvard.
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Theory
In theory, photons, the particles that make light, could be attracted in a nonlinear medium. In test, a laser beam fired into an extremely cold cloud of rubidium slowed down the photons and made them act as a single entity.
Fiction
Solid light appears in many video game franchises, including Halo, Portal, Mass Effect and Overwatch. (Warframe?)
References
Solid light Wikipedia(Text) CC BY-SA