“Particle” is a catch-all term for words that have no clear part of speech, like “hmm.” (Many English particles are also described as “interjections.”) A modal particle is a word that’s used in speech to convey extra emphasis or emotion, without any real grammatical function.
It’s often said that English has no modal particles, but we have some pretty similar features. Think of asking a small child “What have you got there?” or “What’s your name then?” The there and then aren’t really necessary in those sentences, they’re just a friendly way of expressing interest. Or if you say “Come on now!” to express disbelief or frustration, the now isn’t strictly necessary. Some other examples are a little more old-timey: “What ever are you talking about?” or “I’ll get him but good.” Notice that all these words have ‘ordinary’ usages apart from their use as particles; this is also the case for the German particles below.
In any case, the exact definition of a modal particle is complicated, but hopefully you’re getting the idea. For our purposes, let’s just define them as any common verbal flourish in spoken German. (Another way to think of them is as ‘verbal emoticons.’) You’re going to hear a lot of these if you talk to native speakers, so it’s useful to know them. Some can have different emphatic meanings, so they appear under more than one heading below.
Das ist wohl wahr!
That’s certainly true!
Das ist ja eine tolle idee!
That’s really a great idea!
Na klar komme ich!
You bet I‘m coming!
Du bist doch nur zugekifft.
You're just [saying that because you're] high.
Q: Das ist doch nicht dein Ernst, oder? A: Doch!
Q: You’re not being serious, are you? A: I am!
Dass ich das gerade von DIR höre...
That I'm hearing that from YOU (of all people)…
Gerade heute musste es schneien!
It had to snow today (of all days)!
Ich versuche, eine Antwort auf eben die Frage zu formulieren.
I'm trying to find an answer to [just] that very question.
So ist es eben. / Es ist eben so.
That's just how it is.
Naja, was hast du erwartet?
Ah well, what did you expect?
Ich war halt besoffen.
(What can i say?) I was drunk.
Das war aber nett von dir!
That was nice of you! [I wasn't expecting it]
Ist das etwa für mich?
Is that for me?
Wie alt bist du denn? [to a child]
So how old are you?
Guck dir das mal an!
Take a look at that!
Das ist schon viel!
It’s more than you think/more than it seems
Du bist ja blöd!
Are you ever dumb!
Das ist aber völliger Quatsch!
That's complete nonsense!
Wie konntest du nur?
How COULD you?
Was hat er sich nur dabei gedacht?
What WAS he thinking?
Was will er schon von mir?
What in the world does he want from me?
Was soll das nun bedeuten?
Now what’s that supposed to mean?
Es war halt ein Vorschlag.
It was just a suggestion.
Wait a sec.