We have 2 objectives: (1) To show you how modals move. (2) To learn the modals.
(Practice the movement till it is second nature to you. Having a 'knowledge' of how they move, without being able to do it in your sleep is of little value when you have to talk.
1 - Modal movement.
Let's use the modal KAN and take it through its paces. The other modals do the same thing, so focus on KAN for a while. When you are comfortable with KAN, it is time to try WIL, MAG, and MOET.
Present Tense: (Add KAN)
Ons lees die storie. > Ons kan die storie lees.
Comment: Just like the helping verbs 'het' for the past tense and 'sal' or 'gaan' for the future, KAN takes the second place, and the verb moves to the end.
Ons sal die storie lees. > Ons sal die storie kan lees.
Comment: In other Germanic languages, the 'kan' will also get booted to the end, but it will be even after 'lees', so remember, it goes to the end to join the verb, but stays before the verb.
Ons het die storie gelees. > Ons kon die storie lees.
Comment: KAN morphs to KON and no further past tense markings are needed.
Kon means past.
Practice: Add KAN to the following sentences in present, future, and past.
1. Ons luister na die radio.
2. Ester drink appelsap.
3. Ben speel die tromboon.
2 - The Modals
KAN (can); SAL KAN (will be able to); KON (was able to)
WIL (want to); SAL WIL (will want to); WOU (wanted to)
MAG (is allowed to); SAL MAG (will be allowed to); MOG (was allowed to)
MOET (has to); SAL MOET (will have to); MOES (had to)
Note: I have to sing > The TO is not translated with modals
I want TO sing > I wanna sing. > Ek wil sing.
I have TO sing > I gotta sing. > Ek moet sing.
Because modals are so frequently used, memorize these words first and automate their use in all three tenses.