Question

When I use to or than after modal verbs?Thanks

Answer 1

Modal verbs (can, could, may, might, will, shall, would, should and must) are followed by infinitive without 'to'.

Semi-modal verbs (used, ought, need, dare) are followed by a to-infinitive:

• They used to live by the sea.
• You ought to know that by now.
• Do you need to use the hairdryer?
• He didn't dare (to) look back.

Answer 2

Could you rephrase your question since neither "to", nor "than" is a modal verb, but "to" is a preposition and "than" is conjunction&preposition.