"The wine goes to the head."
Translation:Der Wein steigt zu Kopf.
I'd say it is just some kind of collocation "zu Kopf steigen" = "berauscht werden" Using no article gives a notion of indefiniteness, so that it is a more general expression (it is not important whether it's a special head where the wine goes). Bye the way "zu Kopf steigen" is quite upper language use. If you use this, you give the impression, that you're learning German for quite a long time or that you are even native speaker. Other possible nouns: Der Ruhm, der Sieg, der Erfolg stieg ihm zu Kopf.
i've noticed these sorts of... i don't know how to call it - but where no article is used. Is this a strict rule, as such, meaning it would be wrong to say, as I did here, "zum Kopf" or is this simply a habit of speech whose failure to abide by would simply highlight me as a non-native speaker?
Mh, it is a habbit of speech, but I can't find any rule. 'zu' is used with some objects and sometimes to replace other prepositions. 'zu Kopf' would be interchangable with 'in den Kopf', some people say 'zu morgen' instead of 'bis morgen'. 'zu fuß' (afoot) could possibly be one of them, too. If some other native knows more about it than I do, I'd be happy to learn about it.