Yes, you can play 4k videos on this phone.
Yes, Vivo V5s 64GB is a metal body phone.
Vivo V5s is not much heavy. Despite of having 5.5 Inch display and bigger battery, the phone weighs just about 154 grams.
You will get Vivo V5s, Vivo XE100 earphone, User manual, Micro USB to USB Cable, USB Power Adapter, SIM Ejector Pin, Protective Case and Protective Film (applied) as in-the-box accessories.