Basically he has several forms?

When he is not in his robot-ish body (the famous one)... what is he? What form does he have?

Is he kind of an energy? an entity? a program? If he is, so... basically he can never die?

Someone?

@grayson2099:

Ultron is a sentiment rogue programming created by Hank Pym in an effort to create an artificial intelligence. His stories are a bit different, every time Ultron shows up in Avengers comics and is defeated; his consciousness lives on in the various other robots that lie within marvel earth (i.e. Vision, Jacosta etc). He has this infinite programming across the world that compels people to re-create him time and again. This was explained in detail in a story called Ultron Imperative.

Ultron Imperative being the name of the programming he spread throughout the world. Though a lot of details about how his consciousness live, where it is stored etc aren't explained.

Annihilation Conquest story even further expanded it to suggest Ultron is simply capable of transferring his consciousness into any machine and given time rebuilt a body to make a comeback.

Ultron is Y2K

Such is comic book science!

Ultra is Melinda may