Is for example an opening adjective?

"For example" is not an adjective. It is a phrase that acts as an adverbial phrase, introducing an example or illustration.

Here's why:

* Adjectives modify nouns (e.g., *big* house, *red* car).

* Adverbs modify verbs, adjectives, or other adverbs (e.g., *quickly* run, *very* big, *extremely* quickly).

* Adverbial phrases are groups of words that function as adverbs.

In the sentence "For example, I like apples," the phrase "for example" tells us that what follows is an example of something mentioned earlier (presumably, a list of things the speaker likes). It modifies the entire sentence, indicating the purpose of the following statement.