I've never tried the metal spout that is available for the NATO Jerry can. I do have a plastic one that came with one of my cans that works OK. I don;t use it much, since filler port on my antique truck is made to work with the plain Jerry can without a spout.
I was thinking of ordering one of the metal ones for my every day can, but from your report, I'm now wondering if that's a waste of time. Do you recall what brand your spout is? Was it leaking at the gasket, or in the spout itself? Leaks at the seal are not uncommon. It's important to make sure things seat properly when closing the lid or adding the spout - especially the first few uses with a new gasket.
I was thinking of ordering one of the
Valpro flexible metal spouts, since they are one of the original Jerry can manufacturers. They cost a bit more than the knock offs, but I was hoping the quality would be decent. Now wondering if I should just live with the plastic one (until it breaks).