I immediately noticed that the inside of the can was coated with something. Checked it with my meter (on resistance) and found that the inside surface of the can will not conduct electricity, so we're not talking about bare metal.
This can of tomatoes was put out by Hunt's...perhaps some cheapo brands cut corners and don't use the coating, but I've seen it in a lot of veggie cans when I open them.
Tomatoes are very acid, by lining the cans they extend the storage life.