Jag måste duka bordet innan gästerna kommer.

Because måste is a modal verb. In Swedish, modal verbs are followed by the bare infinitive, without att.

So:

• Jag måste duka bordet = I must set the table

Not:

• Jag måste att duka bordet ❌

Other common modal verbs work the same way:

• kan = can
• vill = want to
• ska = will / am going to / should
• får = may / am allowed to

For example:

• Jag kan duka bordet
• Jag vill duka bordet

Duka bordet is an idiomatic expression meaning to set the table.

Word by word, duka has the idea of laying out things for a meal, and bordet means the table. But in natural English, you would normally translate the whole phrase as set the table, not something more literal.

A useful contrast:

• duka bordet = set the table
• duka av bordet = clear the table

So the small word av changes the meaning a lot.

Because bordet is the definite form of bord.

• ett bord = a table
• bordet = the table

In this sentence, it is a specific table that both speaker and listener understand, so Swedish uses the definite form.

This is very common in Swedish. Instead of using a separate word like the, Swedish often adds the definiteness to the end of the noun:

• bok → boken
• hus → huset
• bord → bordet

Gästerna means the guests. It is the definite plural form of gäst.

The pattern is:

• en gäst = a guest
• gäster = guests
• gästerna = the guests

In this sentence, the speaker means specific guests who are expected to arrive, not just any guests in general.

Because Swedish often uses the present tense to talk about the future when the time is clear from the context.

Here, innan already shows that the guests have not arrived yet, so kommer naturally refers to a future event:

• innan gästerna kommer = before the guests arrive

This is very normal Swedish.

Other examples:

• Jag ringer dig imorgon = I’ll call you tomorrow
• Vi åker på fredag = We’re leaving on Friday

So present tense in Swedish often covers both present and planned future situations.

Because innan introduces a subordinate clause, and subordinate clauses in Swedish do not follow the main-clause V2 word order.

Main clause:

• Gästerna kommer snart = The guests are coming soon

After a subordinating word like innan, att, när, eftersom, om, the subject normally comes before the finite verb:

• innan gästerna kommer

So the structure is:

• Jag måste duka bordet = main clause
• innan gästerna kommer = subordinate clause

Yes, absolutely. That sounds natural if the context already makes it clear that you mean set the table.

So both are possible:

• Jag måste duka bordet innan gästerna kommer
• Jag måste duka innan gästerna kommer

The version with bordet is a little more explicit. The shorter version is more conversational if everyone already knows what is being prepared.

Innan means before.

Here it connects two actions:

• first: Jag måste duka bordet
• second: gästerna kommer

So the sentence says that the first action has to happen earlier than the second one.

Innan can be used in two common ways:

• before a clause: innan gästerna kommer
• before a noun phrase: innan middagen = before dinner

Sometimes, but the meaning changes a little.

• måste = must / have to
• behöver = need to

So:

• Jag måste duka bordet innan gästerna kommer = I must set the table before the guests arrive
• Jag behöver duka bordet innan gästerna kommer = I need to set the table before the guests arrive

In many situations, they are close in meaning. But måste often sounds a bit stronger and more necessary.

Also note a grammar difference:

• Jag måste duka = no att
• Jag behöver duka is possible, but many speakers also say Jag behöver duka bordet naturally in this kind of sentence

A rough guide:

• Jag ≈ yahg or yah
• måste ≈ MOH-steh
• duka ≈ DOO-kah
• bordet ≈ BOOR-det
• innan ≈ IN-nan
• gästerna ≈ YES-ter-na
• kommer ≈ KOM-er

A few extra notes:

• å in måste sounds somewhat like the vowel in British more, but shorter.
• ä in gästerna is like the vowel in air for many learners, though it is not exactly the same.
• Swedish r varies by accent, so do not worry if yours is not perfect yet.

Yes, it is completely natural and idiomatic.

A Swedish speaker would easily say this in everyday life, especially when preparing for visitors.

It sounds practical and normal, and all parts of it are standard Swedish:

• Jag måste = I have to / I must
• duka bordet = set the table
• innan gästerna kommer = before the guests arrive

So this is a very useful sentence pattern to learn.