However I did notice, everywhere I had any metal
(galavanized) there is not any mold for a path all the way down the roof
underneath. I guess it is the Zinc in the metal that kiils the mold.

Correct, it is the zinc. You can buy rolls of zinc sheet metal to
install under an upper course of shingles to give your entire roof this
protection against moss and fungus.

--
is Joshua Putnam
http://www.phred.org/~josh/
Books for Bicycle Mechanics and Tinkerers:
http://www.phred.org/~josh/bike/bikebooks.html