Maybe, maybe not. There's no shortage of iron or aluminum ores. Aluminum metal is valuable to recycle because it's so easy to recycle, and uses so much energy to produce from ore. Iron does not take an exorbitant amount of energy to produce from ore and it can be produced with coal instead of electricity. However, if we get steep carbon taxes, that will drive up scrap iron prices because recycling iron saves lots of carbon use.... every day 90% of us send some kind of metals to the land fill will this cause a shortage some day ?
Even copper, which is much more rare than aluminum or iron, is needed mostly for electrical purposes. While we're not getting rid of electrical equipment, the biggering and biggering of electrical consumption may end soon in the developed world (less heavy industry, and residential 200AMP services look a little funny with LED bulbs and other tech), and there's some evidence that the developing world will leapfrog most rural electrification. The economics of copper certainly don't justify $140 rolls of 14/2 romex.
So, yes I throw way too little bits of metal into the scrap pile, but logically it doesn't make sense unless it pays. If we need it sometime, the stuff in the landfill will still be there.