Question: I've recently been watching some streamers on TwitchTV. I noticed sometimes they used a higher pitch at the beginning of a sentence for content/important words. 

For example in a conversation between two people, I heard "**I'm** good today", "**I'm** done with you", etc.

Normally, if I'm right, it should be "I'm **good** today", or "I'm **done** with you." (This is what I have learned at school).

So I assume that this kind of intonation must serve some specific purpose right?

Thanks guys.

Answer: 
Yes, it means *I'm* good today, but I can speak only for myself; perhaps you or everybody else is, or I don't know if you or anyone else is-but as for me, *I'm good*. Perhaps you're not. (Or I could imply that it seems you're not, but I am not saying this explicitly.) More context could help determine the exact connotation. 

Likewise, I don't know about anyone else but *I'm* done with you. Maybe Joe's not, better ask him. But I am.
When a word is emphasized vocally this way it is known as a *pitch word*. 

[What are pitch words:](https://pronuncian.com/pitch-words/)

> 
> Pitch words are the single most important word of an intonation unit
>  in a spoken English sentence. They are given more vocal emphasis than
>  any other word in the intonation unit and also use pitch changes to
>  convey subtle meaning. - Pronuncian.com
> 
> 
> 

You create a pitch word by altering the pitch of the word, the length of the word or the volume of the word, or any combination thereof. 

***Normally, if I'm right, it should be "I'm good today", or "I'm done with you." (This is what I have learnt from school)***

There is no right or wrong with pitch words, the words you pitch affect the meaning of your sentence subtly, so the decision about which words to emphasize in this way will be dependent on the meaning you wish to express. 

Taking your example (using bold to indicate the pitched word): 

> 
> "**I'm** good today"
> 
> 
> 

The above intonation places stress on the word *I'm*. The listeners attention is placed mostly on the individual speaking, the *I* of the sentence. 

How does this impact meaning? Well, the listener is now focused on the speaker, and presumably about what they are going to say next about themself. Also this stress places emphasis on the pronoun of the sentence, it would make transitioning into a sentence where you want to place emphasis on another pronoun more natural, e.g: 

> 
> **I'm** good today... How are **you**?
> 
> 
> 

In this case the pitch word is being used to *contrast* between two things, this is a common use of pitched words. 

Taking your second example: 

> 
> "I'm **good** today"
> 
> 
> 

Here you can see that the emphasis (emphasis is another common use of pitched words) is on the quality of state that the person is experiencing - they are feeling *good*. The listeners attention is placed more squarely on the experience that the speaker is having, and less on them as an individual. 

In addition to emphasis and contrast, [pronuncian.com](https://pronuncian.com/pitch-words/) list two other uses for the pitched word: to *highlight new information*, and to *show uncertainty*. 

You can listen to audio examples of the four main uses: 

1. Emphasis.
2. Highlighting new information.
3. Showing uncertainty, and
4. Contrasting.

At the page linked above.