Most meeting planners ask for a motivational speaker video before hiring a professional speaker.
In any interaction, people need to know what you want. Most conversation involves some kind of objective - there are very few neutral interactions - and the thrust of the interaction is typically understood by those involved, even though it is not stated.
There are some amazing motivational speakers with a compelling message. I think a really good professional speaker has a refined speaking style. Below are some of those styles to help you decide which would work best for your conference experience.
The question I get alot is how do you become a Motivational speaker? The best answer is you just do it. Speak alot, everywhere they will listen, even if you are speaking for free ( however if someone wants to pay you, take their money). Once you get good at it ( 500 plus presentations later) usually people will ask you if you do this for other events,or for a living, and it builds from here.