Reduction of Metals in Packaging Act - Prohibits the intentional introduction of lead, cadmium, mercury, or hexavalent chromium into a package or packaging component during manufacturing or distribution. Sets forth the maximum allowable concentration level of the sum of such elements in packaging. Makes such prohibition inapplicable for packaging: (1) that was manufactured prior to this Act's effective date; or (2) that would not exceed maximum concentration levels but for the addition of recycled materials. Provides for two-year exemptions from requirements for packaging to which lead, cadmium, mercury, or hexavalent chromium has been added to comply with Federal health or safety requirements or, because it is essential for the protection, safe handling, or function of the package contents. Permits for the renewal of exemptions. Requires packaging manufacturers or suppliers to furnish certificates of compliance (with respect to this Act's requirements) to purchasers. Makes certificates of compliance available to the public upon request. Authorizes the assessment of civil penalties for violations of this Act.