This is exactly the case where Wikipedia comes in handy, here are some quotes from the article on 3D printing with metals:
Direct metal laser sintering (DMLS) is an additive manufacturing
technique that uses a laser as the power source to sinter powdered
material (typically metal), aiming the laser automatically at points
in space defined by a 3D model, binding the material together to
create a solid structure.
The DMLS process involves use of a 3D CAD model whereby a .stl file is
created and sent to the machine’s software. A technician works with
this 3D model to properly orient the geometry for part building and
adds supports structure as appropriate.
Currently available alloys used in the process include 17-4 and 15-5
stainless steel, maraging steel, cobalt chromium, inconel 625 and 718,
and titanium Ti6Al4V. Theoretically, almost any alloy metal can be
used in this process once fully developed and validated.