Metal 3D printing remains a goal of the additive manufacturing community. While the technology is in development, it's still a ways off from becoming a common household holding. Students at Delft University of Technology, inspired by R&D progress at Michigan Technological University, are working toward the creation of an open source metal 3D printer. The printer in development effectively combines an MIG welder and a Prusa i3 printer to 3D print metal objects, tethering the MIG welder to the machine in place of a typical extruder and hotend. Successful tests have already taken place, though print speed is considerably slower than traditional plastic-based 3D printers. Check out more details about this up-and-coming technology in the full article:

Below is a picture of a 3D printed test object, a wall-like structure made of metal: