We present generalized hybrid surface-integral-equation formulations for three-dimensional conductors with arbitrary shapes. The proposed formulations are based on flexible applications of the electric-field integral equation and the magnetic-field integral equation with varying combinations on different regions of the given objects. As a proof of concept, we demonstrate hybrid formulations using two-region maps and their parametric analysis. We show that hybrid formulations may enable optimal solutions in terms of accuracy and efficiency, in comparison to the conventional CFIE implementations with fixed combination parameters.