I keep mine in the sacks with the tops rolled closed. They sit in a dark hallway closet. Specialty grains and whatnot, are in the bags they came in, in storage bins in the same closet.
Vittles vaults for base malt (2 row, Pilsner and MO) sacks and 5 lb or smaller Munich, Vienna & crystal and like malts in their original packaging- the kind of VV that have the spin on/off lids with Gamma seals and can hold a full sack; then Rubbermaid tub for bags of flaked grains and dark roast, rice hulls, etc…
I have heard of the metal trash cans used, also (for those place with sharp toothed critters) - I would definitely keep the grains in their original packaging with that set up!
In the original sacks, spun closed, inside big Rubbermaid bins. Mice can and will chew right through the grain sacks. I don’t like any headspace above the grain; I think it makes it go rancid faster.
I buy bulk 2-row and store it in two 5-gallon food-grade buckets with Gamma Seal Lids (Amazon.com).
I keep my specialty grains, malts and adjuncts in Better Homes and Gardens Square Flip-Tite Storage Container (Robot or human?) that hold 5 lbs of grain.