Here in MN, we often see metal trim cladding over older wood window trim casing and window sills. This is covering older, usually moisture damaged windows.
Anyways, when the sills are properly sloped, and the seams in the cladding are properly lapped (like shingles) would you recommend sealing these joints with an exterior caulk?
Around here they have a habit of wrapping porch beams with metal…I know of at least one case where a roof leak or drip back got onto the porch beams which was wrapped with metal and it rotted it out completely. Typically when wood is wrapped with metal on three sides it could allow the moisture to get trapped and the damage can be extensive; but because it is wrapped it’s hard to detect. Wood that can’t dry out rots at a much faster rate.