New insight into the mechanical behavior of thin metallic films on substrates can be obtained by a novel experimental technique. It comprises stress measurements by the wafer curvature technique in combination with a four-point bending of beam-shaped samples. A dedicated apparatus was constructed which allows such experiments in high vacuum between room temperature and 500 °C to be carried out. It has a stress measurement sensitivity better than 0.1 MPa and a long-term stability better than ±0.2 MPa over 24 h in the case of a 1 μm thick film. Strains up to 0.8% could be imposed by a four-point bending on films grown on 380 μm thick Si substrates before cracking of the substrates. Both the thermal cycling and the four-point bending technique were used to investigate the plastic behavior of 1 μm thick Cu films on oxidized Si substrates.