Here's what I have for you!
Lucky you! You're level 40! The first ores, copper and tin, are easy-peezy to find. For coppe,r I highly suggest the Gol-Bolar Quarry in Dun Morogh (the zone outside IF). There are about 3-4 spawns inside it, 3 or so in in the quarry basin area, and 4-5 in the area outside and around the quarry.
Tin, I loved the Redridge Mountains (east of Elwynn Forest, the newbie human area). There are copious tin and copper veins in the caves of the area; run a loop around the entire zone a few times. You can your damned travel form >_>. Oh, I guess you'll have a mount too :-P.
Next, we have Iron. Yes, I'm skipping silver, it's a rare tin spawn. Iron... is totally Thousand Needles. Hands down my favorite place. Check the caves in the area (there are also mithril spawns). Note: Irons randomly spawns gold, and mithril randomly spawns truesilver. Once you learn the spawn locations (approximate), you'll have no problem finding these in this zone. There are also two iron and maybe 2 tin spawns around the edges of the SHimmering Flats. Again, yay for your mount/travel form :-P. And in the buggy area, there are always two mithril spawns (ooze-covered).
That's as far as I am, it should work for you :)