[palmer]

Why would they heat a rock

Because rocks are in the vicinity or behind or beneath practically everything.

As for the cars burning and the wheels melting, that happens usually on the downwind side of the car. Here's one partly melted wheel in a parking garage in Chicago:

One thing lacking in your explanation is how a directed energy weapon melts wheels. It would take a lot of weapon time on target to do that, as opposed to just lighting the car on fire and moving on.

[editor-surveyor]

,
No, in every case shown so far it has been all 4 wheels.

And not just a little melt, but a puddle where the wheel once was. Sometimes running across the street for several feet.

In addition, both aluminum and magnesium ignite very close to their melting point. Aluminum often vaporizes.

[editor-surveyor]

I can weld with very little power.

Just plug into a standard 20 amp circuit,