If one were to fill the fuselage of an aircraft with helium gas, how would that effect it's flight capabilities?

Say I pumped a large drone, full of helium. Would it still be able to zip around, or would the lift from the helium stop it from normal operation?

Or. Would you have a drone, that could do all the normal drone stuff, but also have to use far less/no power, to hover if it’s not moving?

I understand the extremely hypothetical nature of the question. I understand that filling a 747 with helium, won’t make it float.

I’m talking about an aircraft, designed to say test proof of concept.