Very simple, name a metal, it can be an element, you can do a google for an obscure alloy, whatever, just name a metal, it allomantic power, it's feruchemical power, (and optionally it's hemalurgic power)
Osmium, the densest metal ever, when burned, gives the burner the power to read the thoughts of others, Feruchemically, it stores Literatic (a word I word-smithed from Literature) skill, when storing, you can't read, you can't write, and things like figures of speech elude you, when tapping, you read blazingly fast, you can write blazingly fast, and you have a fanstastic grasp of your language, and all of it's figures of speech.