1 - will: It
will rain tomorrow. (uncertain, no proof)
2 - shall: Shall I buy eggs? Shall we bring you coffee? (offer, only ‘I’ and ‘we’)
3 - to be going to: I'm going to see my aunt on Saturday. (plan, proof: appointment on Saturday)
4 - present simple as future: The plane leaves at six. Fixed schedule, for buses, trains, school, etc.
5 - present continuous as future: My mother is having a party at home tomorrow. Fixed, time and place.