Accumulated evidence clearly demonstrates the influence of attached microorganisms in an array of natural and engineered processes, e.g. biomineralization, microbially influenced corrosion of metals (MIC), biomining, and bioremediation. Our knowledge of the mechanisms behind these interactions is limited because they are complex, and because we lack suitable model systems to study the interactions. We have been studying ennoblement of stainless steel - a phenomenon that can lead to a specific yet pervasive form of MIC. Biofilms on stainless steels constitute an ideal system to study microbe-metal interactions, since the redox reactions involving biofilm and stainless steel are relatively slow. Progression of the processes can be easily monitored in real time, since rates are significantly limited by the electrical properties of the passive films.