In this letter, we report a modified percolative polymer composite that has a low dielectric loss (tanδ∼0.02@10KHz, comparable to that of the polymer matrix), a high dielectric constant (k>100@10KHz, about 30 times higher than that of the polymer matrix), and a low frequency dependence. This high-k polymer hybrid is filled with self-passivated micro- and nano-aluminum particles. The self-passivation of an aluminum particle results in dense nanoscale insulating Al2O3 shells outside of the metallic spheres, which allows the electrons in the metallic core to tunnel through it, and thereby the aluminum/polymer composites exhibit a high dielectric constant as a percolation system; on the other hand, the insulating oxide layer restricts the electron transfer between aluminum particles, thus leading to a very low loss of the composites.