I am aware that the lithium is a chemical element (a metal, more precisely), but I was wondering if it is commonly used as a metaphor in English language? Maybe to describe a situation or a sentiment, or in some other way. What made me think about this is that two of the song that I like are named "Lithium" (by bands Nirvana and Evanescence), without any apparent connection to the literal meaning of the word. I just want to point out that I am not asking the explanation of the lyrics of the songs, I am just wondering about the metaphorical usage of the word "lithium" that you are familiar with, since I couldn't find anything googling.
Wikipedia has an article (Lithium(medication)) explaining that lithium salts are commomly used to treat major depressive illnesses.