This article provides an insight into the radiation emission during laser beam welding of aluminum and steel alloys. The core issue is the development of a system to monitor the welding process of challenging alloys with respect to their chemical composition in the melt pool. To reduce welding faults, like cracks, brittle phases or other metallurgically based faults, a high degree of process knowledge is necessary. This manuscript presents novel spectroscopic investigations used to analyze laser beam welding setups to gain insight into the process. The results were attained by processing common alloys of today’s manufacturing applications. The results of these measurements allow an insight into laser welding techniques in consideration of designing a suitable process monitoring system. This empirical results are accomponied by theoretical considerations about the excitation degree of different alloying elements. Together they are a progressive step to develop a system to control the chemical composition of the melt pool during the active welding process.