weather stripping/ foam strip?
Those foam strips they sell you to go under the ridge caps will eventually dry out, blow out, and be hanging all over the place. Caulking won't fill a 5/8's gap to keep the wind/rain out, and tar has no place whatsoever on a metal roof, you'll get it all over everything, and either one will look like ****. The best ridge cap has to be custom made and cut to fit. I use a 12" wide X 10' strip, bent in half to pitch, and then turn down 90 degrees on the edges, whatever the rib height is, usually 5/8". Hold the ridge cap in place on the ridge and mark where the ribs are, then notch out for the ribs so that the cap sits flush over the ribs and down on the flats, punch holes and screw down thru the tops of the ribs. It's a little time consuming but it makes for a good looking finished product that won't wear out.
I'm assuming your talking about a ridge cap normally you would seal it in with tar or polyurethane caulk and put your shingles over it
