At least here in the western United States, we almost never use "tin" any more, except for perhaps a "tin of sardines." (Even this expression is not as common as it probably once was. I hear people can "a can of sardines" too). Tin is a type of material (chemical symbol Sn). If pressed, I would say "can" refers to almost everything that is cylindrical in shape (such as a can of soda, beer, soup, but NEVER, at least not here, a tin of soda, beer, or soup). A tin to me almost implies an odd, non-cylindrical shape, such as that square tin of sardines that I previously mentioned. Also, if the can is made from tin, you can call it a "tin can," but most soda cans are made of aluminum today.

Today "Tin" and "Can" are synonymous in British slang "Have you got a tin [beer]?" or, "I think I'll have a tin of beans." This usage is fairly well established and I was able to find the news headline "Rat Found in Tin of Beans" online just moments ago. In this usage, "tin" refers to what was historically the most common material for can construction. The move toward aluminium hasn't displaced this usage much in the UK. In American English, the phrase "a tin of..." meaning a metal container, was never as widely used as in the UK. As mentioned, "Tin Can", meaning the sort of can soda and beer come in, fell out of use shortly after aluminum became prevalent here.

These are not synonyms. Tin is a metal, a material. Can is an object which is often made from tin (or was in the past). So, while a "wall made of cans" and a "wall made of tin" could be the same wall it is only because "cans" can be made of "tin".