Modal verbs features: Modal verbs have more than one meaning: I can swim ability

Ought to is possible instead of should:

It’s really a good film. You ought to go and see it.

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  Should is also used to say that something will probably happen:
  

A: Do you think you’ll be late home tonight?
B: I don’t think so. I should be home at the usual time. (=I’ll probably be home)

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  If something should happen means If something happens. You can use both structure. But with should the speaker is less certain:
  

If you should see Tom this evening, can you tell him to phone me?

You can also begin with should (before the subject) :

Should you see Tom this evening, can you tell him to phone me?

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  You can use should after these verbs:
  

suggest propose recommend insist demand
They insisted that we should have dinner with them.= They insisted that we had dinner with them.

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  You can use should after these adjectives:
  

important strange funny natural surprised essential odd typical interesting surprising
It’s strange that he should be late. He’s usually on time.
I was surprised that he should say such a thing.