What is this sound coming from under the truck brand new 2018 honda ridgeline after I did the wheel alignment?

When I back up It has that quick initial metal stretching sound and I only noticed it after the alignment was done. What is it and how should I fix this?

Should not have needed a wheel alignment on a brand new truck. But at least you have a bumper to bumper new vehicle warranty, take it back to the dealership

The bigger question is why are you doing an alignment on a new vehicle?
Suspensions make noise after the vehicle is up in the air until the weight of the vehicle settles on the wheels.

Take it to the dealer. They will likely ask you what exactly are you doing with the truck.

Go back to the shop and tell them to check it. Maybe they left a wrench in the suspension. They'll be glad to get their tools back. Once I found a pair of vice grips clamped to my sway bar and had no idea how long it had been there.