An improved approach for implementing metal fill on an electrical device without causing creating cross-coupling capacitance problems is disclosed. Timing aware metal fill insertion is performed to avoid or minimize cross-capacitance problems on the IC design. A cost may be assigned to different candidate metal fill shapes. The cost is associated with the expected effect upon timing requirements by the metal fill shape, with lower costs corresponding to lower expected impacts upon the timing requirements. To meet density requirements, lower cost metal fill shapes are inserted prior to higher cost metal fill shapes.