Aluminum cans and thermite?!
Answers: i heard something about aluminum cans containing another kind of metal and would it be safe to use aluminum cans as an ingredient in thermite if there is another kind of metal made with it????
Aluminum cans are pretty much made of aluminum. They would not be a good ingredient in thermite. You would need something hotter than a potasium nitrate / sugar mixture to ignite it.
The other metal you've probably heard of is Magnesium, not a whole lot of magnesium in cans.
Filing doen aluminum cans (which are pure aluminum) takes a long time. Filing down pure magenesium (which is an alternative to aluminum in the thermite reaction) is extremely dangerous and expensive.
I recommend just buying them already in powdered form. Go to www.unitednuclear.com and click on the chemicals and metals link. You do not even need a license to buy them there!