Another spout for the NATO jerry cans.
 
This is the one we use. It has just enough flex at the end to make for easy fueling in hard to reach spots. It even comes with hardware to attach the spout to the can when the spout is not being used.
 

I too use a metal 5 gallon gas can.

No spout.

Just a little trigger like device opens the can cap and pour. Sometimes I have my wife hold a funnel and sometimes I just pour very slowly directly into whatever needs filling and rarely spill a drop.

I refuse to use those impossible plastic POS cans sold everywhere. Sure, they're much less costly, but the cost to your bp is way up there as they are such a giant pain in the ass to use.

I got mine from Amazon.

Most of the 5 gallon plastic cans we have don't have vents. Takes long time to fill tractor along with spillage since flow comes in spurts.

Drilled small hole toward top and inserted a plastic wall anchor. Fits perfectly, snug fit, but easy to remove when filling. Provides a nice even flow, no more spillage.