A downhole apparatus for use in a tubular include a mandrel, a first slip, a cone, and a seal element. The mandrel, which can be permanent or temporary, has a first end shoulder. The first slip is disposed on the mandrel adjacent the first end shoulder, and the cone is disposed on the mandrel adjacent the first slip. The cone is movable relative to the first end shoulder to engage the first slip toward the tubular. The seal element is disposed on the mandrel adjacent the cone. At least a portion of the seal element is composed of a dissolvable metallic material and is expandable outward from the mandrel. The expanded portion of the seal element forms a metal seal against the tubular and seals off fluid communication in the annular space between the seal element and the tubular.