A device for feeding gas in a melt of foamable metal by means of at least one pipe for producing metal foam. The gas insertion pipe projects inwardly into the melt and at the projecting end has a gas outlet having a cross section of 0.006 to 0.2 mm.sup.2 and a pipe face area of less than 4.0 mm.sup.2. A flowable metal foam has gas bubbles defined by walls of a liquid metal matrix with solid reinforcing particles, and the diameter of the largest gas bubbles divided by that of the smallest gas bubbles is less than 2.5.