horses for courses.
I use saba 750XL sealant/bonder (from my local chandlery) for sticking panels in place (holds well but can be removed by inserting a saw blade), expanding polyurethane for non-critical joints and epoxy mixed with fibre additive to a peanut butter consistency for permanent structural weathertight bonding and joints.
saba grabs well on metal and wood, but needs clamping or a temporary screw or two, to stop the panel moving down under gravity for an hour or so.
polyurethane has no grab, doesn't stick well to metal, and needs needs clamping against expansion (the glue fills any gaps very well).
epoxy sticks almost anything, has no grab and needs clamping.