Yes they can 3D print in metal (jet engine turbine blades), ceramic, all sort of plastic. As you see they’re more and more complex as well. Soon we’ll have home fabricators painting your next car.
Wouldn't metal have to be in a semi-liquid state for the printer to form it into the proper state? I don't see how they could do that with steel that would have to be heated to a superhot state.
It’s powder and they sinter it. I think they use a titanium alloy for the jet engine blades. The printer can actually make shapes that can’t be machined. GE has a video on the process as they make the turbine blades. Here you go https://www.ge.com/reports/mad-props-3d-printed-airplane-engine-will-run-year/