Humans have been working with metal to make tools and weapons for thousands of years but I can't think of how they could have extracted the metals in the first place.
Ancient people weren't nearly as stupid as many modern people think. They extracted the metals basically the same way we do today - they mined ore and smelted it.
Of course, in the beginning (~7000-5000 BC) it was mostly ore chunks recovered from the surface as opposed to ore chunks from underground veins, but eventually they did in fact mine ore from underground. In fact, some of the earliest mines are at [Rudna Glava in modern Serbia](https://en.wikipedia.org/wiki/Rudna_Glava_(archaeological_site)), and date to ~4000 BC. And by 3800 BC you had copper mines in the Sinai peninsula (such as Timnah) that have also been excavated.
Your next question will probably be "But how did they get the metal out of the rocks?"
Again, the same way we do today. They started off with surface mining, getting chunks off the surface, using rocks and metal tools to knock pieces off of surface outcrops of ore, then using the resulting metal tools to mine deeper (the same way you use stone to get iron in Minecraft, then use that iron to get more iron).
A couple websites for an introduction to the topic:
http://pages.ucsd.edu/~dkjordan/arch/metallurgy.html
http://www.historyworld.net/wrldhis/PlainTextHistories.asp?historyid=ab16
Northern Europe, and Scandinavia in particular was rich in what's called "Bog Iron" (sometimes differentiated as "Lake Iron" depending on where it's found). Rocky iron deposits get eroded and washed down from the mountains, accumulating in bogs and lakes. The iron reacts with the acids in the bog into insoluble compounds that precipitate out, as well as through bacterial processes, thus concentrating it. Bog iron is much easier to get to than subterranean deposits because nature has already done the extraction. The Russians were still dredging Lake Onega to get bog iron for the iron works at Petrozavodsk into the 1800's.
For a basic explanation, see here.
For a more in-depth look, see Buchwald's Iron and Steel in Ancient Times
hi, FYI you'll find some additional information on this topic in the FAQ
