Modalpartikeln - what the heck are they?

Throughout the course I have been puzzled by words that seem to be thrown into sentences at random, but don't change the meaning such as ja, denn, mal etc.

Then I came across this Easy German video:  https://www.youtube.com/watch?v=-Awhco_VHWE&t=358s

then I found that if you google Modalparikeln you get quite a lot of hits, here are a couple:
http://languagelearningbase.com/88440/modalpartikeln-german-filler-words
http://germanforenglishspeakers.com/other/modal-particles/

My German grammar book doesn't even mention them, but these links helped me understand what they are about if not exactly how to use them all.
 

Hi sfpugh,

Modalpartikeln, at least some, can be compared to the function that "do" has in "I do like reading", for example. English doesn't use these kinds of intensifiers as often though, so they might be confusing.
There is really no strict rule on how to use them, and are usually found in informal situations.

Lucia

Thanks Lucia, As far as I can see, using modal particles is a pretty high level skill and should only be used by people who are already fluent.
However they do crop up quite often in Level 3 and occasionally in level 2 so it would be nice to have a short piece on them in one of the grammar sections in level 3 explaining what they are.
Personally I found them very confusing until I discovered the video on them.

I wouldn't want to try and use them myself though except perhaps ja as an intensifier and mal to make imperatives more polite.

Hi Lucia have pick out a few examples of what I think may be modal particles that appear in the course. I wonder if I got them right?
Mensch, die ist aber  braun. - Look, she has a wicked tan.
Das hat aber gut geschmeckt! - This tasted great!
Aber so sehe ich eben Deutsche. - But that's how I see Germans in a way.
Oh warte mal, hier ist ja mein Reisepass! - Hang on, there is my passport!
Sag mal, sind die beiden denn gläubig? - Tell me, are those two religious?
Das ist ja interessant. - That is interesting.
Was darf es denn sein? - What would you like?
Wo drückt dich denn der Schuh? - Where does the shoe pinch you? (What's troubling you?)
Worum geht es denn? - What is it about?
Naja ein wenig. Politik interessiert mich halt nicht sehr. - Well a little. Just not very interested in politics myself.