Det kommende møtet er viktig.

Because møte is a neuter noun in Norwegian.

• en / den are used with common gender nouns
• et / det are used with neuter nouns

Since the basic noun is et møte, the definite phrase with an adjective becomes det kommende møtet.

Compare:

• den store bilen = the big car
• det store huset = the big house

So here, det matches the neuter noun møte.

The ending -et marks the noun as definite singular.

With this noun:

• et møte = a meeting
• møtet = the meeting

So møtet is simply the definite form of møte.

Yes — and that is normal in Norwegian. This is often called double definiteness.

When a noun is definite and has an adjective before it, Norwegian usually uses:

• a definite article before the adjective
• a definite ending on the noun

So:

• møtet = the meeting
• det kommende møtet = the upcoming meeting

This is standard Norwegian structure.

Kommende comes from the verb å komme and is used like an adjective here. It means something like coming or upcoming.

So det kommende møtet literally has the sense of the coming meeting, but in natural English it is usually the upcoming meeting.

Because kommende is a participle-type adjective in -ende, and words of this type usually keep the same form.

For example:

• en kommende uke
• et kommende møte
• de kommende dagene

Unlike many regular adjectives, kommende does not change to match gender in these examples. The form stays kommende.

Because viktig agrees with the noun møte, which is neuter singular.

Compare:

• en viktig dag = an important day
• et viktig møte = an important meeting

In your sentence, the subject is det kommende møtet, and the head noun is still møte, so the adjective becomes viktig.

If it were plural, you would get:

• Møtene er viktige = The meetings are important

Yes. In Norwegian, adjectives can agree with the noun even when they are used predicatively — that is, after verbs like er.

So:

• Møtet er viktig
• Boka er viktig
• Husene er viktige

Even though viktig/viktige comes after er, agreement still matters.

Yes. This is a very normal Norwegian main clause:

• Det kommende møtet = subject
• er = verb
• viktig = predicate adjective

So the pattern is:

Subject + verb + complement

It looks very similar to English here.

Yes. That is very natural Norwegian.

There is a small difference in feel:

• det kommende møtet = the upcoming / coming meeting
• det neste møtet = the next meeting

In everyday speech, det neste møtet is often more common. Kommende can sound a bit more formal or written.

Not in standard Bokmål if you want a definite noun phrase with an adjective before the noun.

You can say:

• møtet = the meeting

But if you add an adjective before it, standard Norwegian wants:

• det kommende møtet

So kommende møtet by itself is not the standard form here.

No. In this sentence, det is not the pronoun it.

It is part of the noun phrase det kommende møtet, where it works as the definite article/determiner for the neuter noun.

So the sentence is not built like It is important.
It is built like The upcoming meeting is important.