Some people memorise their whole presentation. Some people read the whole speech. Both of these approaches have their advantages and disadvantages. But most people use a compromise and, if possible or necessary, use notes.
Two very important parts of your speech are the opening and the closing. If you memorise those you can be sure you will use the words you chose for the greatest impact, and you can concentrate on delivery and especially on eye contact. You can choose to read them, but you will need to find other ways of giving them power. You probably should also memorise the punch lines of your jokes, and any words you are quoting verbatim.