I have seen too many of these:
  • Introduction slides that give away the entire story of the presentation (and the speaker spends 20 minutes on it)
  • Summary slides that repeat the entire story of the presentation (and the speaker spends 10 minutes on it)
Delete them both.
The first slide should just cover what you are about to say, but not say it. The last slide should be an uplifting graphic reminding people about your key messages. Repeating these messages will just bore your audience.