The commentary provides technical explanations and supplementary background information on the new Parts 2 and 4 of DIN EN 1090 "Execution of Steel Structures and Aluminum Structures." The newly revised Part 2 of DIN EN 1090 has led to the development of Part 4, which comprehensively addresses the technical requirements for load-bearing, thin-walled, cold-formed components and parts made of steel. The requirements of the two parts of the standard are explained section by section and illustrated with practical examples. In addition to the interrelation with the Eurocodes, the commentary also addresses legal implications for construction in Germany and Europe, international contexts, and historical engineering references.