A modal verb is the one that gives you the clue of what the speakers want to say, I mean, it's a way of saying something; in this case, haow to express obligation or necessity:
- I have to lose some weight --- I have a necessity of losing weight
Sometimes the modal is also an auxiliary verb but sometimes it isn't as it happens with HAVE TO; besides, a modal can change its meaning depending if you use it in afirmative, negative or interrogative form:
- I can play here (I'm allowed) I can play the piano (I know how to do it) I can't play the piano here (It's forbidden-prohibition) Can I play here? (I ask for permission)
Here you are some links about modals of obligation and some of them also have exercises at the end: here you have one of them with a chart so click
here; this one is with the form
ought to, a form that is not very used, click
here; or this one in which other modals are included, click
here
If you want to practise, you can do these exercises:
For those who want to improve their English in the future, you can use this site with many more possiblilities, but it's for a much higher level; click
here.
See you in class!