Alloys which are a mixture of two or more metals, can you used widely in all areas.
First of all,,, the alloy formed will have different properties and characteristics to the metals which were mixed to make the alloy.
Also, alloys are stronger, because it is impossible to actually cut an atom, ( possible but you know what i mean = X ) what happens is that the smaller metal's atoms, goes in between the larger ones, hence as you cant cut an atom, the alloy is made stronger.
Common alloys include :
Stainless Steel, ( very useful )
Or aluminum alloys.
They are used for all sorts of stuff, as when different metals are combined ( mixed ) with other metals, they form new properties which may be useful in different areas.