Adding chimney flashing to a metal roof is a bit different than flashing a shingle roof. In both cases, however, it is necessary to seal the area around the chimney to prevent water leakage, which can severely damage your home. On many metal roof installations, a rubber-like water/vapor barrier is put into place before the metal roofing is installed. This is an excellent product to help seal the roof and chimney. A metal roof uses the same type of chimney flashing—sheet metal—as that used with a shingle roof. It is installed the same way as on a regular shingle roof as well.