The purpose of a main idea is to meet standard publishing guidelines show what the overall story is about make readers spend more time analyzing give people something to write about

The purpose of a main idea is to "show what the overall story is about". At this stage of the process, details are usually left out for the most part. 

Dr.king , i would take my mental flight by egypt and i would watch god’s children in their magnificent trek from the dark dungeons of egypt through, or rather across the red sea, through the wilderness on toward the promised land.his  speech"i  have a dream" to encourage people that change will come. this  speech  was very important during the civil rights movement and was a contributing factor in the end of racial injustice in society. the  intended audience  of "i  have a dream" is white people. i hope this