My feed is kept in a metal trash can with a lid. I don’t usually get moths in my bin, but I’ll get flies. They can be slipping in while you’re feeding, or if there’s a side of the lid that isn’t flush.
I don’t think a few moths are necessarily A bad thing, but I don’t know for certain. If there was a bunch in the can, you might want to scoop off the top layer of grain. I’d look into how they’re getting into the can. You may need to get a new container, maybe a plastic trash can with a solid locking lid.