Wow. Wolverine 17 asked if a light will mount on a Shield and it's turned into a mounted-light vs. hand-held light debate LOL.

Wolverine 17, the Shield does not have a rail. There is a flat portion where a rail would normally be, but it is flat. I don't believe the frame is wide enough for a standard rail. Crimson Trace will probably eventually have one of their tac-lights that mount to the trigger guard, like for other makes and models, as others have already mentioned. You will just have to buy two M&Ps. A Shield, of course, and one of the other models with a rail .