What's on the Moon?
Distinct Regions
If we look at a general image of the Moon, like the one above we can see distinct regions on the Moon. In general we talk about two distinct regions, the lighter areas we call the Highlands, and the darker areas we call the Mare or Maria (from the latin for 'seas'). In general, the Highlands areas consist of more aluminosilicates such as anorthite, that is to say they have a higher concentration of aluminium. The Mare tends to be more basaltic and has a higher concentration of iron in the form of iron-bearing minerals like pyroxene.
Looking closely at a colour saturated image of the Moon, like the on here by Rich Addis, we acn actually see that the maria can actually be subdivided again into two further regions, the high titanium and low titanium mare. This is of significant interest when looking into the geochemistry of future feedstocks for astrometallurgical processes, but we won't go into that much detail here. If you're interested in geochemistry then have a read of "The lunar regolith: Chemistry, mineralogy, and petrology" by Papike et al. (1985), it's got everything.
"Ball of Rock" © Rich Addis
Silicon
Starting off strong with a resource that is technically not a metal, but important, nonetheless. Silicon is both prevalent and extremely useful. It can be used to make silanes, a form of rocket fuel, or as a generic 'energy carrier'. But most importantly it's used a lot in electronics and will be very valuable in making photovoltaic panels for energy generation.
Aluminium (or Aluminum)
Again, as one of the more prevalent metals on the Moon, aluminium will be very valuable as a construction material. It's light weight and strength make it very useful for construction and manufacturing. Interestingly aluminium becomes even more useful when we alloy it with other metals, while we're somewhat more restricted on the Moon, we can still explore alloying with elements like: Si, Fe, Mn, Mg, Ti, Ca, and Na. In addition to these uses, using aluminium as an energy carrier and/or as a type of energy storage has also been proposed.
Iron
Iron is the bread and butter of construction on Earth, so luckily, we still have access to it on the Moon. What makes iron special is actually how 'easy' it is to make; it takes a lot less energy to make iron than most other metals making it a great material to use in construction and manufacturing. We often get fancy with iron and alloy it with other metals to produce more desirable physical and chemical properties.
Magnesium
While not normally the first metal that rolls off the tongue, magnesium can be a really useful metal when it comes to alloying with other metals like Al and Fe. Like aluminium, magnesium is lightweight and quite strong, it's used terrestrially in some manufacturing but the difficulty with it is that it is very reactive and will oxidise quickly when exposed to atmosphere, luckily on the Moon, there's no atmosphere. So it has been proposed that we could actually use magnesium as a bulk construction material in its own right. Weather that ends up happening or not is yet to be seen. As with a lot of the metals on this list, it's also been proposed that Mg could be used as an energy carrier or storage material or even as a solid rocket fuel in a pinch.
Titanium
While slightly limited in is concentration in most regions on the Moon, as explored above, there are some areas that have quite high concentrations of Ti. Titanium can be used as a construction material either as a pure metal or alloyed with other elements. And again as a way of storing energy.
Manganese and Chromium
These metals are perhaps slightly less well known, however as in the field of metallurgy they're extremely useful. While hard to use on their own, both manganese and chromium are great for alloying with the major metals to produce alloys with favorable properties.
Sodium and Potassium
Perhaps not what we think of when we normally think of a metal, sodium and potassium are nevertheless potentially quite useful. They're relatively easy to reduce (in terms of energy requirements) and can be found in reasonable quantities in some rocks on the Moon. These elements can of course be used as a form of energy storage, and sometimes alloyed with other metals, but one of the more novel ways they can be used is together as coolant material. The alloy of Na and K (NaK) has a very low melting point making it a great liquid coolant or hydraulic fluid in some applications. On its own potassium can even be used in plant fertilisers, although that may be a use for the more distance future.