Making real things, from a computer program is not new, it is still, and has been for at least my working life of 30 years, it is called CNC milling, other names are about, Computer Numerical Control. yes 3D printing can make metal parts too, Airbus and Rollls Royce pehaps use this.
Very true, though CNC cuts out the required piece from a larger block rather than building it up in layers. I have not studied the more modern 3D printing, but with CNC there were / are physical limits as to what shapes could be produced due to the physical access from the tools. Looking way back, I was involved with some early computer programming - cutting out aerofoil section moulds for ceramic inserts to shape turbine blade cooling chambers. The maths of producing the final shape, and to the correct tolerances, with a round nosed tool travelling up and down still makes my head hurt!