How and when do we use each of the English modal verbs?

Uses of "might" (negative: might not)

1. As a past from of "may"
   "The weatherman said it might rain."
   "She mentioned that she might come."
   "We agreed that it might be dangerous."
2. To show possibility (it is slightly weaker than "may")
   "He might pass the exam, but I wouldn't count on it."
   "We might fail, but let's not think about it."
   "I might visit on Saturday."