This is not a question of syntax, which is the study of the manner in which phrases and sentences are constructed. Furthermore, "would and will" are not analogous to "may and might." In many usages, perhaps most usages, may and might can be used interchangeably. Would and will are very disticnt. Will deals with a certainty or an alleged certainty. Would refers to a condition. So, for example, i might say "He will be there on Saturday." But if i say "He would be there on Saturday." i imply that there is a condition. "He would be there on Saturday, if
he gets his work completed on time." The word "if" in that sentence, introduces the condition--that he gets his work done on time. In saying he will be there on Saturday, i am stating, or alleging, a certainty, which is not governed by any condition.