Metal forming is a series of techniques in which metals are plastically deformed and they include: impressing, rolling, extrusion and forging. Upsetting of metals is considered a type of forging. In this master's thesis, basic terms related to metal forming such as permanence of volume, degree of deformation, speed of deformation, plastic yield stress and energy of deformation are described in brief. Technology of forging with an emphasis on upsetting is portrayed as well. Procedure of upsetting with free axial deformation of cylindrical samples made of three aluminum alloys is analyzed. Upsetting force needed for deforming cylindrical samples is calculated using maximum plastic yield stress and mean plastic yield stress for different values of logarithmic degree of deformation. Listed analyzed procedure is also processed experimentally where cylindrical samples are firstly subjugated to free axial deformation caused by an impact of gravitational hammer and then deformed on hydraulic press. Upsetting energy was monitored in the part of the experiment that includes gravitational hammer and upsetting force was kept track of in the part of the experiment that includes hydraulic press. Analytical and experimental results are compared in this master's thesis. With the help of MSC Marc Mentat software, procedure of upsetting all three cylindrical samples made of different aluminum alloys is simulated with a goal of showcasing stress distribution and geometrical shape of upsetted samples.