An executive once urged his staff to give him the third paragraph first. It was his way of asking them to go directly to the point and not to include a bunch of background information.
There is a similar rule in writing fiction. Although we have chronologies beaten into us in high school, novelists often start their books with what could have been the third chapter. It gets readers into the action early and the other information can be added later.
So too with presentations. Plunge your audience into a compelling part of the subject. Get them swimming around in the swamp. Make them aware of the gators and the snakes and then push a canoe their way.
Unless the beginning is really interesting, don't make it the beginning.