Gluing / Welding plastic questions

[Bobby Bourgoin]

Greetings;
I want to build a EG-6 / GNK Power Droid, and as a base for the body I have two Sterilite containers made of Polypropylene. Was is the best way to glue / weld / fix polypropylene to polypropylene, metal, and polystyrene?

Thanks
Bobby

for those interested I have a Facebook page about my droid builds which curently contains my modified MSE mouse droid; Bobby's Droid Factory