"Light is composed of photons, so we could ask if the photon has mass. The answer is then definitely "no": the photon is a massless particle. According to theory it has energy and momentum but no mass, and this is confirmed by experiment to within strict limits"

How can photons have energy when E=mc^2? If m=0, then E=0.

What am I missing?

(I just randomly though about photons and wondered if they had mass and googles it, and then found quotation above)