I use plastic bins with hinge lids for feed - they fit two 50 lb bags and can stack on top of each other - $8 each on sale at Wilco. Portland has a big rat problem and I've trapped a few in the run, and so far, there have been no chews through either the plastic bin or the plastic home depot buckets I use for BOSS, Flax seed, etc. No issues with galvanized metal when using plastic, totally waterproof/rustproof, and they're cheaper, too.
The rats did eat through a paper bag of treat parrot feed, which is when I started storing everything in plastic.
Both Portland and Seattle have serious rat problems; on the wharves in Seattle I swear there were rats that seemed almost as big as possums.
NO, they were definitely NOT possums.
Get a good rat terrier. Both cities suffer from an pseudo-environmental complex that prevents them from taking the needed steps against rats. Both allow people
to set up feral cat colonies to save an invasive, dangerous species. It is NOT true that if colonies are removed other feral cats will move into the
area - colonies permit them to survive in concentrations 10 - 100 times as dense as normal conditions.
Why do I single out feral cat colonies? If you stay in an area where there are feral colonies, the rats tend to swarm the feed after dark. They will
literally drive the cats off of it. There used to be one near the marina in Redwood City, CA, and the concentration of rats seeking that feed was
like something out of a horror movie if you had to pass it after dark. We had a little Catalina 22, and we weren't comfortable sleeping on it
after dark because of the abundant rat supply. Most cats will not take on rats, you can spot the ones that do because when hunting, they
make moves like a boxer.