Kool Seal would work, and if the roof is metal you can use the regular Kool Seal instead of the RV version (which is for use on EPDM roofs).
Dyco #890 is another such product. but a Lowes or Home Depot will have a selection of products for metal roofs. Henry's is another top name in the roof coating arena.
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL