Metal cans can, if not vented in some way, burst if left in the sun or implode if they are allowed to cool off. Due to the hazards involved, in some organizations, they are not legal to have in the pits. I know they are strictly forbidden to have in the pit area at R/C Unlimiteds events for those reasons. Since I've been running Powermaster, which comes in cans, I've had to transfer the fuel into a plastic fuel jug before taking it into the pit area and transfer the left over fuel back into the can for storage before heading for home.