Answer:
The metaphor "cashing a check," from Martin Luther King’s speech “I Have A Dream,” literally means to get an amount of money promised to you when you cash a check. Here, it is used to point out that the United States had promised something to African-Americans and they have come to get what the US had promised to give them.
Step-by-step explanation:
Martin Luther King through his speech wanted to encourage the African-Americans to fight for their rights – the rights that the government owned them. He began his speech with a question that concentrates on what the US promised the African-Americans. He also mentions what it promised - all men irrespective of one’s colour would be guaranteed the rights of life, liberty and happiness. But they were segregated. They faced racial discrimination. The use of this metaphor makes King's speech more effective because it draws the people to the main point of the speech.