In "I want the following: butter, sugar, and flour" "the following" seems a "direct object", "following" seems like a verb. I thought nouns seem like objects?
An object does not necessarily have to be a noun. They can be nouns, pronouns, phrases, or clauses. Here are some examples:
- I want cookies. (direct object = noun)
- I want to work. (direct object = verb phrase)
- I want that. (direct object = pronoun)
- I want you to stand up for yourself. (direct object = clause)
You can see that a direct object can take many forms. In your sentence, however, it is a noun. More specifically it is an ing-form of the verb to follow used as a noun. You can often use ing-forms as nouns:
- The fighting led to arrests.
- Closing up prevents any more customers from entering your shop.
Note that the ing-forms used as nouns do not necessarily take an article.
If you want to learn more about ing-forms, you can take a look at this page.
"the following" is elliptic and stands for "the following things". When "the following" is used without "things" we must see it as a noun, meaning everything that follows. Probably used only before enumerations.