Improvement in resistance spot welding quality in sheet metal do have significant implications on the automotive manufacturing process. This paper reports on our recent effect to gain a fundamental understanding of the weld development process. A simple physical model, based on the dynamic resistance curve is presented describing the resistance changes during the process of weld development. In addition, a series of electrical and metallurgical measurements were performed to capture the temporal behavior of the weld resistance in terms of its component elements. Since the interface resistances are most affected by weld variables such as welding force and electrode cap wear, these interfaces can be major sources of weld quality variation. The results obtained provided a novel yiew of the sheet-metal welding process.