When we talked about tenses, we mentioned helping verbs -- a word added to go along with the verb to flag the future (sal/gaan) or past (het ge-) tenses. When a present tense sentence is made past of future, the SAL for future and the HET for Past Tense takes that all important second position where the verb was, and the 'real' verb goes to the end of the sentence.
Modals are helping verbs too. When adding a modal to a present tense sentence, it takes the second position from the verb and the verb goes to the end of the sentence. And yes, you can get two helping verbs in a sentence, one to indicate the tense, and then a modal helping verb to indicate the 'mood'
Afrikaans modals are regular and English ones are not. In the lessons on modals, you will see what I mean. The modals are KAN (can), WIL (want to), MAG (may), MOET (have to). In case you were wondering, if you have tense and mood helping verbs in the same sentence, the tense goes first, and mood goes to the end with the real verb. Past tense is similar to other Germanic languages in that a modal is slightly changed to indicate both mood and tense. kan > kon; wil > wou, etc.