Replying to Attaching metal pipe to wood same way as you would PVC

Uhm i was at homedepot returning ABS pipe that my friend bought cus hes a dumbass and i told him to buy PVC... neways i was browsing thru the aisles and in one ther was metal fence posts like i dunno maybe 8' for like 10$!!!??? then there was VERY long metal tubing like 15'+ also for fencing for like 15$??? why the hell do ppl even waste money on PVC???? cant u use like metal screws and attach it to the wood same way as you would PVC, im guessing i would need to drill a samll hole first... is this pipe grindable?? would i need to like wax it OR should i just stick with the original plan and go PVC....

thnx