infinitive vs gerund - "look forward to meet you", or "to meeting you"?

Which one is correct?

I look forward to meet you during the coming festival.

or

I look forward to meeting you during the coming festival.

Please help me with explanation.

Answer

There are some set rules, avoiding them will make is sound unnatural or incorrect.

The pattern with look forward to is

Look forward to + Noun

Look forward to + verb-ing

These are set pattern, not following them will make the sentence incorrect.