Jag tar på mig solglasögon så fort solen kommer fram.

The dictionary form is ta på sig, which means to put on (clothes, glasses, etc.).

In the sentence, it appears as tar på mig because:

• ta changes to tar in the present tense
• sig changes to mig because the subject is jag
• Swedish often splits this kind of verb phrase in a sentence

So:

• ta på sig = to put on oneself
• jag tar på mig = I put on myself / I put on

This is very common in Swedish with verb + particle + reflexive structures.

Because sig is only used for he/she/it/they when the action refers back to the subject.

Since the subject here is jag, Swedish uses mig.

Compare:

• Jag tar på mig solglasögon. = I put on sunglasses.
• Hon tar på sig solglasögon. = She puts on sunglasses.

A quick pattern:

• jag → mig
• du → dig
• han/hon/den/det/de → sig

So ta på sig is the infinitive form you learn in a dictionary, but in real sentences the pronoun changes.

Because solglasögon is being used as an indefinite plural noun, and Swedish normally has no article in indefinite plural.

So:

• en bok = a book
• böcker = books

Likewise:

• solglasögon = sunglasses

Not en solglasögon and not ett solglasögon.

If you want to be more specific, you could say:

• ett par solglasögon = a pair of sunglasses
• solglasögonen = the sunglasses

In normal use, solglasögon is treated as a plural noun, much like English sunglasses or glasses.

That is why you say:

• Jag tar på mig solglasögon.

and not a singular form for the whole item.

Very often, things like this in Swedish are expressed as plural or as ett par ...:

• ett par solglasögon = a pair of sunglasses

So for learners, the safest way is to treat solglasögon as a plural noun.

Because the sun is a specific, unique thing, so Swedish normally uses the definite form: solen.

Compare:

• sol = sun
• solen = the sun

In this sentence, we are not talking about a sun in general. We mean the sun that everyone knows about, so solen is natural.

This works like:

• månen = the moon
• jorden = the earth

Here så fort means as soon as.

So:

• så fort solen kommer fram = as soon as the sun comes out

This is a fixed expression. Even though fort often means fast/quickly, in this phrase it does not mean that something happens fast in a literal speed sense.

You can think of it as a time expression introducing a subordinate clause.

A close alternative is:

• så snart = as soon as

Here kommer fram means something like:

• comes out
• appears
• becomes visible

With solen, it usually suggests that the sun comes out from behind clouds.

So:

• solen kommer fram = the sun comes out

The particle fram often adds the idea of something becoming visible or emerging.

Because så fort introduces a subordinate clause, and in Swedish subordinate clauses the word order is usually subject + verb.

So you get:

• så fort solen kommer fram

not:

• så fort kommer solen fram

This is an important difference from main clauses.

Main clause:

• Solen kommer fram.

Subordinate clause:

• ... så fort solen kommer fram.

Also notice what happens if the subordinate clause comes first:

• Så fort solen kommer fram, tar jag på mig solglasögon.

In that version, the main clause has inversion: tar jag.

Because Swedish often uses the present tense for:

• habitual actions
• general truths
• near-future situations

Here the meaning is habitual: whenever the sun comes out, I put on sunglasses.

So:

• Jag tar på mig solglasögon så fort solen kommer fram.

means something like I put on sunglasses as soon as the sun comes out / whenever the sun comes out.

This is very natural in Swedish. You do not need a special future form here.

Yes. Ta på sig is the standard, very common verb for putting on clothes and accessories.

So ta på sig solglasögon is perfectly natural.

Swedish also has other verbs that may appear in specific contexts, but for learners, ta på sig is the safest and most useful general choice for things you wear:

• ta på sig en jacka = put on a jacket
• ta på sig skor = put on shoes
• ta på sig solglasögon = put on sunglasses

So this sentence uses the most useful everyday pattern.