55 gallon drums will eventually rust, and if you cut them, you have an edge you either have to grind down or do something to it to avoid cutting yourself.

I've had good success with old cattle protein tubs. I've had some for over five years now, and they're still in great shape. Drill some holes in the bottom for drainage, and put about 2"-3" of broken up styrofoam in the bottom (keeps the weight down if you ever need to move them). Fill them with a good garden soil, and buy the best one your budget will allow. DO NOT USE POTTING SOIL. I've had good success with tomatoes, cucumbers, peppers, lettuce, and spinach. You just have to remember that you can't overcrowd them. One tomato plant per tub.