lol!
it doesn't SUCK light,
well light posses dual nature , it can act as a particle and as a wave, it does have mass(mass though very small, but I care to mention coz gravity is a property that mass reacts to and people tend to neglect this basic fact).
Now, when we talk about a black hole, its apparent "gravity" is so high, so so high that nothing escapes it, so it ends up absorbing all the light, reflecting back not even a single spectral band! That is the reason we call it a BLACK hole today, coz it looks black for the reason i gave above