Distinguishing metals from nonmetals?
Well as santiago has pointed out, they are all in fact metals. 

The way you can determine if it is a metal or not is that when any metal reacts with acid, hydrogen gas is released. This is shown in this general equation (it is not balanced): $$\ce{M^{m+} + HCl -&gt; MCl + H2}$$

Meanwhile, generally non-metals don't react with acid. This because when a substance reacts with acid, it electrons to the H+ ions created by the acid. Non-metals are generally electron-accepters, rather than electron donors so there is no way for them to donate electrons to the hydrogen ions in the acid.

In your experiment, the bubbles that formed when reacted are indication that hydrogen gas is being formed, therefore the substance is a metal. Therefore, you should be able to tell that Fe, Al and Zn are metals. 

Therefore, you might assume that Sn and Cu have to be non-metals. However they are actually metals. The reason why no bubbling is observed is because these metals are unreactive and don't get oxidised by the acid.