You are correct about "indossare" but "mettere" or "mettersi" is the act of put on a dress and not " to wear "
It rejected "He always wears dark sunglasses." I know sunglasses are "occhiali da sole" but who wears "dark glasses which are tinted to be dark but not as protection from sunlight" hehe.
Yeah, not today anways! It sounds very 1970's, at least in America. I used to have prescription glasses that tinted darker when you went outside.
In Czech, "to wear black glasses" means "to be (overly) pessimistic". And the opposite is "to wear pink glasses". Could this sentence have similar meaning in Italian?
I ran gli occhiali through some on-line translators, and the results indicate very strongly that in this context, the generality of "wears dark glasses" requires the article to be dropped. When it's included, the sentences mostly mean "the specific glasses being worn now" or "those glasses" (without quelli - still gli).
It may have something to do with portare. Since you can only wear one pair of glasses at a time, the lack of the article indicates that the reference is to the glasses - any number of them - which can be worn over a period of time. With the article, the reference is to THE glasses being worn at a particular time.
I will have to pay stricter attention to the nature of the verb action, to see whether this kind of analysis works with other verbs.
For instance, I'd bet (if I did that sort of thing) that io guardo le mucche = "I watch the cows" requires the article, because "io guardo mucche" = "I watch cows" would be really weird and not make much sense.