MTV said Monday that both are due to perform, along with singer Jason Derulo and rappers J Cole and Mac Miller. The night's festivities will be hosted by Tyler Posey of MTV's "Teen Wolf" and Lovato.
The show will air from MTV's Times Square studios. Fans can bid to be part of the audience. Proceeds will go to FWD, to help with the crisis in East Africa.
The show will air live at 11 p.m. EST.