Right now the site finder simply says 'Shallow Metals' or 'Deep Metals' however this can cause a lot of confusion for new players, and frustration for veterans. Especially since 'metals' includes non-metals from gems to microline. You embark on a site that says shallow metals, it's reasonable to expect metals. Not orthoclase. This is worsened by the fact that there are dozens of minerals so many times metal ores don't even have a chance of showing up.
So I propose separating gems, metals, and non-metal minerals in the raws. Each would get their own tag in the raws [MINERAL_GEM][MINERAL_METAL][MINERAL_NON_METAL] respectively. This would make the embark say things like Shallow Gems, Deep Metal, Shallow Non-Metal instead of an ambiguous broad statement. This would allow players to find a more suitable embark sites instead of embarking and praying for an actual metal.
The world generator could be spruced up as well, allowing you to set Gem, Metal, and Non-metal frequency.
This little change wouldn't be to hard to implement, would improve the UI, and would allow players to have a better embarks all around.
On a more modding perspective, it would be nice if there was a [LIST_IN_EMBARK] tag that you could slap onto rocks. It would then show up similar to how it says Flux (but it will work if the stones are a vein, large cluster, or deep in the earth). This would make testing metals and stones much more easier then guessing and checking.