Metal minis are generally made of tin alloys, with or without lead. (There was a lot of talk about lead being used in minis a couple of years ago, so most manufacturers stopped using lead. A few (mostly makers of historical minis) continue to use lead.
Pewter is an accepted name for tin alloys. Ralidium was a (marketing ploy) name used by Ral Partha for their alloy.
And back to the topic.
The survey might need some clarifications regarding whether the questions only relate to use of minis for RPG purposes, or for any purpose. (I'm thinking of question five, primarily.) As I play fantasy, horror, modern and SF minis games (not to mention historical, which should be an option if talking about miniature games), but only use minis in fantasy RPGs, it has some relevance.
Perhaps there should be an option for 3d terrain in the last question, i.e. scale models.