What the sealant should be
The sealant should be stable over a wide range of temperatures, water resistant and adhere to the metal surfaces.
Generally a single sealer strip can be used at side laps and a double line of strip at end laps.
The sealant should also be compatible with filler block materials and at least 12mm wide to ensure that it is not cut through by the fixings.
See also Portfolio outdoor lighting and affordable glass