In this paper, we investigate the crosstalk-induced delay and noise implications of floating and grounded fill metal generated using each of the rule-based and model-based fill placement techniques. We first examine the impact of fill metal on several interconnect test structures, which provide important insights into the performance and reliability implications of both intra-layer and inter-layer crosstalk coupling due to dummy fill. We then explore the noise and delay implications of fill metal on several large-scale designs implemented in 65 nm process technology. For the grounded fill cases, the fill metal significantly reduces crosstalk-induced delay and noise. Designs with floating fill also experience a reduction in average crosstalk-induced delay and noise, which is in contrast to the predictions of previous studies on small-scale interconnect structures.