Metalaffaldet er i posen.

Because Danish usually writes compound nouns as one word. Here, metal + affald becomes metalaffald.

Then the definite ending is added to the end of the whole compound:

• metalaffald = metal waste
• metalaffaldet = the metal waste

This is very common in Danish.

In Danish, the definite article is often attached to the noun as an ending instead of being a separate word like English the.

So:

• -et is a common definite ending for a neuter singular noun
• metalaffaldet means the metal waste

A useful point: in compounds, the last part usually decides the grammatical gender. Here the head word is affald, so the compound follows that pattern.

Because posen means the bag, while pose just means bag.

The basic noun is:

• en pose = a bag

The definite form is:

• posen = the bag

So i posen means in the bag.

Because Danish nouns belong to different grammatical genders.

• pose is a common gender noun, so the definite singular ending is usually -en
  
  • en pose → posen
• metalaffald follows the gender of affald, which is neuter, so the definite singular ending is usually -et
  
  • metalaffald → metalaffaldet

So the different endings reflect the noun’s gender.

Because i posen means in the bag — a specific bag.

Compare:

• i posen = in the bag
• i en pose = in a bag

So the sentence is talking about a particular bag, probably one already known from the situation, such as a recycling bag.

Usually not in this sentence.

For this meaning, Danish normally wants either:

• i en pose = in a bag
• i posen = in the bag

A bare noun like i pose would sound incomplete or unnatural here.

Er is the present tense of at være, which means to be.

So:

• er = is / am / are, depending on the subject

In Danish, the present tense form does not change for different persons:

• jeg er = I am
• du er = you are
• han er = he is
• vi er = we are

So with metalaffaldet, you also use er.

It follows the normal Danish pattern for a simple statement:

• Metalaffaldet = subject
• er = verb
• i posen = prepositional phrase showing location

So the structure is basically:

subject + verb + place

This is very similar to English here: The metal waste is in the bag.

Yes, but Danish main clauses follow the verb-second rule, often called V2.

So you can also say:

• I posen er metalaffaldet.

That still means roughly the same thing, but now i posen is placed first for emphasis. Notice that the verb er still stays in the second position.

Grammatically, it is singular definite.

But semantically, it works like a mass noun, similar to English the metal waste. That means it refers to the material or category of waste, not necessarily to one single item.

So even though the form is singular, the meaning can be more general or collective.

Because Danish does not capitalize all nouns.

Only the first word of the sentence is capitalized here because it starts the sentence:

• Metalaffaldet er i posen.

If the word appeared in the middle of a sentence, it would normally be lowercase:

• Jeg tror, at metalaffaldet er i posen.

You switch the verb and the subject:

• Er metalaffaldet i posen?

That means:

• Is the metal waste in the bag?

This is the normal way to form a yes/no question in Danish.