It is shown that simple face-centered-cubic (fcc) structures of both metallic and coated metallic spheres are ideal candidates to achieve a tunable complete photonic bandgap (CPBG) for optical wavelengths using currently available experimental techniques. For coated microspheres with the coating width to plasma wavelength ratio lc /lp £ 10% and the coating and host refractive indices nc and nh, respectively, between 1 and 1.47, one can always find a sphere radius rs such that the relative gap width gw (gap width to midgap frequency ratio) is larger than 5% and, in some cases, gw can exceed 9%. Using different coatings and supporting liquids, the width and midgap frequency of a CPBG can be tuned considerably.