Metals (cosmere wide discussion)

[PinkPlasma she/her]

Hiya! its me Freya  
So I have been wondering about how the metals (non-godmetals) interact with investure, so I figured we could maybe try and use this thread to theorize a bit and gather up everything we know, because I'm sure there is stuff that I have missed. as far as I'm aware there are 17 metals that interact with ivestiture in the cosmere. 

1. Steel 
2. Iron
3. Pewter
4. Tin
5. Zinc
6. Brass
7. Copper
8. Bronze
9. Duralumin
10. Aluminum
11. Nicrosil
12. Chromium
13. Gold
14. Electrum
15. Cadmium
16. Bendalloy
17. Silver (I'm gonna ignore this one because it seems to be it's own separate thing from the other metals)

The First 16 of these metals are established parts of all 3 metallic arts (allomancy, hemolurgy, and furochemy) I'm gonna try and avoid delving into these because they are their own magic system, and less about the metals themselves and how they interact with the investiture. The 16 Allomantic metals are also established parts in making specific types of fabrials, based on what spren they interact with within a gemstone. We know that alluminum interferes with investiture on the pages in mistborn, warbreaker, stormlight, and Emperors soul. that covers a pretty huge swath of types of investure that we know that this metal interacts with. based on that, you can easily assume that it will probably interact with all other types of investiture, and that the other allomantic metals will interact investiture as well. To put the cherry on top here, I believe we have a couple Words of Brandon confirming this.

So working off of this we can assume that all the first 16 metals, (The allomantic metals) interact with all types of investiture in varying ways. but this is doesn't exactly help us understand what the metals actually do. It's like looking to see if the generator is on in a building, but never checking what it is powering. the information is good to know but not very useful on its own. so we need to list everything we know for sure that a metal does to investiture, either via WOB or on the page confirmation. I'm going to write a small group of stuff I remember and that I think is important. I would love to create a list with all confirmed effects metal has on investiture, with each metal.

A:  Rhythm of War Epigraphs (https://coppermind.net/wiki/Rhythm_of_War/Epigraphs)

The important epigraphs here are 6 through 11, giving us a fairly in-your-face piece of the puzzle. Using these I'm gonna make a couple of assumptions.

1. The categories used in the allomantic table (Push, Pull, and possibly the 4 larger categories, Physical, Mental, Enhancement, and Temporal) are still important to how metals interact. while I would be hesitant to say that the 4 larger categories are going to be the same, the metals within them clearly are. Zinc and brass, along with Pewter and Tin, still have paired effects. from what is said we can easily assume that Iron and Steel are still paired as well, although it hasn't been discovered yet. From these tidbits, we can assume that all the metals that have paired effects in the allomantic table will have paired effects on how they interact with investiture.
2. The effect the metals have, at least on some types of investiture, is a passive effect. the metals in the fabrials don't need to be invested or capital C connected to anything to have an effect, they simply change the investiture that is within close proximity to them, in this case, being pressed up against a gemstone filled with the said investiture. the metal simply has to exist, and it will have an effect. I think this is an important thing to note.
3. The metals will have similar effects across types of investiture, most of the time. the attractor fabrial, made using iron, is incredibly similar to the effect iron has in allomancy. The theorized repelling fabrial, assuming it does use steel, would also have an incredibly similar effect to how it functions in allomancy. Brass and zinc strengthen and weaken a sprens presence, very similar to strengthening or weakening the presence of a specific emotion.

B: Aluminum

Aluminum is seen across the cosmere as a sort of catch-all block to investiture at this point. it's used in fabrials to direct investiture signals by blocking certain connections, and is completely resistant to forgery. aluminum is completely immune to allomantic manipulation from steel and iron, and burning it as an allomancer is essentially the same as pressing ctrl + alt + delete on all the metals, or possibly all investiture, you had inside you (is there a WOB on if burning aluminum would get rid of stormlight or biochromatic breath in your body?). it is possible that aluminum, if thick enough, could block a shardblade. aluminum cannot be lashed or soulcast. nightblood, possibly the most invested object in all of the cosmere, is almost completely contained with just and aluminum sheath, only able to send his thoughts out to those around him. this is another huge point in favor of the third assumption I made with the Rhythm of War Epigraphs.

Tress of The Emerald Sea Spoilers (not major to plotline but still spoilers)

Spoiler

 We saw both iron and steel effect spores while growing, causing them to grow directly away or towards the metal, again supporting assumption 3 as well as assumption 2. I'm not entirely sure if they are the same as investiture however, and think this should be taken with a grain of salt.

That's all I remember without too much digging, however I am certain there is more. Is there any big things that I missed? I have a couple of theories on how certain things like how making an aon out of a certain metal might change how it works, but I'd love to hear other people's thoughts on this stuff.