Laser cutters can cut plywood and other composite wood but because of their glue content, they can't give proper cuts like the one you get from solid wood. There are specially crafted laser plywoods available in the market which can be laser cut evenly and smoothly.
There are laser cutters that are used to cut thick steel, such powerful cutters are dangerous and you'll have to be well-disciplined to work with such machines. The damage caused by these machines will depend on the intensity and the amount of time you're exposed to the laser.