Only four types of metals are listed above. For 6 metal layer design, only these 3-4 metals will be used in alternative way or they use 6 different metals??
All M1-M10 are copper alloy (with small % of aluminum). I think no use aluminum alone now a days because of electromigration issues. Vias are formed using Tungsten.
Copper mainly from M1 to top metal layer. Cu(Mn) Alloy with TaN/Co liner is used to reduce electromigration (Check IEDM 2012 Paper 33.7). Tungsten (W) is used for contacts and vias. Below 28nm node 2 local interconnects are being used (1 to connect M1 to gates and 2nd to connect M1 to S/D) and there is a discussion (I am not sure if foundries are already doing it) of moving the local interconnects to W from Cu.