How do I hang an outdoor metal decoration on siding?

Check Amazon for vinyl siding hangers. They slide under the siding and hold without putting holes in it. They are also removable.

Hi Jill, It depends on how heavy the metal tree is. If it's light in weight, the Command Hooks put on several different heights of the vinyl siding should work. They will keep all the weight from being on one 'panel' of the siding which in turn will keep the siding from being pulled off the porch. If the metal tree is real heavy, you better hang it somewhere else, remember, vinyl siding must be able to expand and contract without any interference so you cannot put anything through it into a wall stud. Vinyl siding is installed by putting small nails through small 1/2" slots and the nails cannot be nailed in tight so the siding can move back and forth via the slots.