I wouldn't assume metal. It's heavy and will rust eventually and require paint touchups. Prefer miltary-grade extra heavy duty plastic from Sceptre. They are only available in Canada for fuel, for water, they can be purchased in the US. It is what is supplied to US military and NATO. They are virtually indestructible and require no maintenance. They have wide mouth lids and pouring spouts with vents and gaskets for both gas or diesel. Check them out online at DS Tactical, near Vancouver, BC. I've used them for 20 years on land and at sea, and have seen no degradation.
Princess Auto also has them. 90 bucks CDN