Kasta inte mikrofonen.

Because this is a command. In Swedish, commands usually start with the imperative form of the verb.

• kasta = throw!
• Kasta mikrofonen. = Throw the microphone.

So Kasta inte mikrofonen. literally follows the pattern:

• verb + inte + object

That is the normal way to make a negative command in Swedish.

In Swedish negative commands, inte normally comes after the imperative verb.

• Kasta inte mikrofonen. = Don’t throw the microphone.
• Compare: Spring inte! = Don’t run!
• Prata inte så högt! = Don’t speak so loudly!

So English says don’t throw, but Swedish says more literally throw not.

It is the imperative form, used for giving orders, instructions, or requests.

For the verb att kasta (to throw), the forms are:

• infinitive: kasta
• present: kastar
• imperative: kasta

Many Swedish verbs in -a have an imperative that looks the same as the infinitive.

Because mikrofonen is the definite form: the microphone.

• en mikrofon = a microphone
• mikrofonen = the microphone

Swedish often adds the definite ending directly to the noun instead of using a separate word like the.

Here:

• mikrofon
  • -en → mikrofonen

The -en ending marks the noun as definite singular for many en-words.

Since mikrofon is an en-word:

• en mikrofon = a microphone
• mikrofonen = the microphone

This is a very important Swedish pattern:

• en bil → bilen
• en bok → boken
• en mikrofon → mikrofonen

It is understood, not stated.

In Swedish commands, you usually do not say the subject. So:

• Kasta inte mikrofonen. means (You) don’t throw the microphone.

This is similar to English commands:

• Sit down.
• Don’t move.

The you is implied.

By itself, it can be used for one person or more than one person in modern Swedish.

The imperative form kasta does not change for singular/plural in everyday modern Swedish.

So Kasta inte mikrofonen. can mean:

• Don’t throw the microphone. (to one person)
• Don’t throw the microphone. (to several people)

Context tells you who is being addressed.

Yes. Släng is another common verb meaning throw.

• Kasta = throw
• Släng = throw / toss

In many situations, both work. But there can be a slight difference in tone:

• kasta is a neutral, standard word for throw
• slänga can sometimes feel a bit more like toss or chuck

So Kasta inte mikrofonen and Släng inte mikrofonen are both natural, depending on tone and context.

A rough English-friendly guide is:

KAH-sta IN-teh mee-kro-FOH-nen

A few helpful notes:

• kasta: the a is broad, closer to ah
• inte: usually IN-teh
• mikrofonen: stress is on fon → mi-kro-FO-nen

This is only an approximation, but it can help you get started.

Yes, grammatically it is possible, but ej is less common in everyday speech.

• inte = the normal everyday word for not
• ej = more formal, written, official, or sometimes old-fashioned

So:

• Kasta inte mikrofonen. = natural everyday Swedish
• Kasta ej mikrofonen. = more formal or stylistically marked

For most learners, inte is the one to use.

Yes. This is a very useful pattern:

imperative verb + inte + object / rest of sentence

Examples:

• Öppna inte dörren. = Don’t open the door.
• Rör inte telefonen. = Don’t touch the phone.
• Glöm inte nycklarna. = Don’t forget the keys.
• Säg inte det. = Don’t say that.

So Kasta inte mikrofonen is a great model sentence to remember.