Memorizing your presentation or speech may seem to make sense but it’s almost never a good idea.
First, when you write a speech on paper, memorize it, then deliver it orally, you are delivering words that were actually meant to be read, not spoken. There’s a difference in how language is used in written versus oral form, and it’s ineffective to try to use one in place of the other.
Second, if you memorize, your delivery (unless you are a very rare exception) will be flat and lifeless, and audiences will see you as distant, cool, and even untrustworthy
One reason people memorize speeches is they don’t want to screw up, or get things wrong, and don’t want to rely on their own brains to operate on the spot. It’s understandable, but there’s other ways to assist yourself through notes, props, etc so you stay on track and don’t appear stiff to the audience.
If you need a half measure to help you particularly at the beginning of a speech when nerves tend to be worst, you might consider memorizing the first three or four sentences of your presentation, just to get you started, and then move to using notes only for guidance.
