Metto una sedia in più vicino al tavolo.

Metto is the 1st person singular, present indicative of mettere.

So it means:

• I put
• I am putting
• sometimes even I’ll put, depending on context

Italian uses the present tense more broadly than English, especially for actions happening now or very soon.

Because in Italian the verb ending already tells you the subject.

• metto = I put
• metti = you put
• mette = he/she puts

So io is usually omitted unless you want emphasis or contrast:

• Metto una sedia... = neutral
• Io metto una sedia... = I’m the one putting a chair...

Una sedia in più means an extra chair or one more chair.

The expression in più means extra / additional.

Examples:

• un bicchiere in più = an extra glass
• due persone in più = two extra people

So here una sedia in più means you are adding another chair to the existing setup.

Not quite.

• in più = extra, additional
• più = more, or part of a comparison

This matters because:

• una sedia in più = an extra chair
• più vicino = closer

A learner might momentarily confuse in più vicino with più vicino, but they are different structures.

Because vicino normally uses a before a noun.

So the structure is:

• vicino a + noun

And since a + il contracts to al, you get:

• vicino al tavolo = near the table

Other examples:

• vicino alla porta = near the door
• vicino ai bambini = near the children

Al is a contraction of:

• a + il = al

Italian often combines prepositions with definite articles:

• a + il = al
• a + la = alla
• a + i = ai
• a + gli = agli
• a + le = alle

So vicino al tavolo literally comes from near to the table.

Here, vicino is functioning like a preposition/adverb, meaning near.

In this use, it does not agree with the noun:

• vicino al tavolo
• vicino alla finestra

But vicino can also be an adjective:

• la sedia vicina = the nearby chair
• le sedie vicine = the nearby chairs

So in your sentence, it is not describing sedia as an adjective; it is introducing the location.

It is understandable, but many native speakers would probably choose a slightly smoother version.

Possible alternatives:

• Metto un'altra sedia vicino al tavolo.
• Aggiungo una sedia vicino al tavolo.
• Metto una sedia in più vicino al tavolo. — understandable, but a bit clunky

Why can it feel slightly awkward? Because in più and vicino come next to each other, and for a moment the listener may expect più vicino (closer).

So if the meaning is I’m putting an extra chair near the table, a more natural option is often:

• Metto un'altra sedia vicino al tavolo.

Yes. In Italian, the present tense often covers a near future action, especially when the action is immediate or already decided.

So Metto una sedia... can mean:

• I’m putting a chair...
• I’ll put a chair...

The exact meaning depends on context and tone.

For example:

• Aspetta, metto una sedia vicino al tavolo.
  = Wait, I’ll put a chair near the table.

Often yes, but there is a small nuance.

• un'altra sedia = another chair
• una sedia in più = an extra chair

Un'altra sedia is usually the more natural everyday choice.

Una sedia in più puts a bit more focus on the idea of addition: one chair more than before, or more than expected/needed.

So both can work, but in più emphasizes extra more clearly.