Commercial aluminium and stainless steel sheets were used as substrates for thin film silicon solar cell deposition. The influence of elemental contamination and disturbed film growth on solar cell performance and yield were studied. Diffusion during film growth was found to be more pronounced than thermally activated interdiffusion of existing films. Surface irregularities of the substrate are shown to reduce the fill factor of the solar cell. Initial efficiencies of 8.5% with single-junction amorphous silicon solar cells on both types of metal sheets were reached.