From Loki: Season 1 Episode 3: ‘Lamentis’ (1×03) | Produced by Marvel Studios (Disney+)

Full lyrics of the song Loki is singing:

Men trærne danser og fossene stanser
Når hun synger, hun synger “kom hjem”
Men trærne danser og fossene stanser
When she sings, she sings “come home”
When she sings, she sings “come home”

Men trærne danser og fossene stanser
Når hun synger, hun synger “kom hjem”
Men trærne danser og fossene stanser
When she sings, she sings “come home”
When she sings, she sings “come home”
When she sings, she sings “come home”
When she sings, she sings “come home”

I stormsvarte fjell, jeg vandrer alene
Over isbreen tar jeg meg frem
I eplehagen står møyen den vene
Og synger: “når kommer du hjem?”

Men trærne danser og fossene stanser
Når hun synger, hun synger “kom hjem”
Men trærne danser og fossene stanser
When she sings, she sings “come home”
When she sings, she sings “come home”

The lyrics translated to English (by LyricsTranslate):

But trees dance and waterfalls stop
When she sings, she sings “come home”
But trees dance and waterfalls stop
When she sings, she sings “come home”
When she sings, she sings “come home”

But trees dance and waterfalls stop
When she sings, she sings “come home”
But trees dance and waterfalls stop
When she sings, she sings “come home”
When she sings, she sings “come home”
When she sings, she sings “come home”
When she sings, she sings “come home”

In storm-black mountains, I wander alone
Over the glacier I make my way
In the apple garden stands the maiden fair
and sings, “When will you come home?”

But dance and the waterfalls stop
When she sings, she sings “come home”
But dance and the waterfalls stop
When she sings, she sings “come home”
When she sings, she sings “come home”