Fiatboy,
I would keep aluminum cans (beer, energy drink, soda, tea) together with pie/take out aluminum containers and used aluminum foil. Usually food cans (campbell's, vegetable, or sketti O's, etc) are steel. If a magnet sticks to it, do not put it with the aluminum cans... pepperpump is correct the scrap yards will get real mad. The one I got to will take high power magnets to the cans until they know you and check the bags. I don't add try to add weight to it... with steel... thats not good. You want the guys to trust you. I you want a little extra weight to the bags, drop them off on a rainy day. I have a pick up and I keep my bags outside, so I get a little extra water weight.
Usually the steel food cans I throw in the town recycle bin. I called the other day and steel scrap prices in the south suburbs of Chicago is between $150.00-$200.00 a ton. I don't have the space, I don't want a pile of rust in my backyard (nor does my wife)! Or I put the steel in a box to the curb, because I have 3 steel scrappers that drive their pickups around here on garbage day, figured I'd help them out.
If the cans are made of tin, that might be worth looking into. I'm not sure about that though, call your scrap yard and ask them, they'll be happy to let you know.
Just have a nice magnet with you. If it doesn't stick, it's probably worth good money.
silver colored metals :aluminum, stainless steel, nickel plated brass or copper, silver
yellow brass, bronze, and copper too are great.
hope this helps, sorry if I rambled on. I'll be happy to help if you have more questions, let me know.
Rumblebelly