When Should We Use 'Shall'?
The modal verb Shall is not used so much. You can still find it in formal speech or some legal documents.
Usually you use Shall in questions thah suggest or offer.
Suggestions -> Shall I get a sushi for dinner tonight? (can be replaced by should)
Instructions -> What shall I do with your parcel when it arrives? (can be replaced by should)
Offers/Volunteering -> Shall I carry that bag for you? (can be replaced by can/could)
Confirmation -> I shall meet him at 3 p.m. (can be replaced by will)
Promises -> You shall be the first person to know. (can be replaced by will)