The influence of mechanical stress on magnetization processes in an amorphous metal alloy have been investigated. The rapidly quenched amorphous metallic ribbons with nominal composition Fe73.5Cu1Nb3Si13.5B9 (precursor of FINEMET) were chosen for this study. The significant differences in the magnetic properties of the studied material were observed at different degrees of mechanical stress applied to the sample. The origin of these effects arises from changes in the dynamics of domain walls. They are primarily caused by variation of their fundamental properties (thickness, energy per unit area of the domain wall) as well as changes in the properties of internal stress areas, which are obstacles to their movement. Impact of stress areas was demonstrated by analysis of influence of mechanical load on the internal demagnetization factor.