Aligning the world...

I’m a tad confused… when using matrix operations (either opengl or my own)translate and rotate ect… I can either set the identity matrix each time or not…when choosing to set the matrix on each draw, do I have to ,at the programs beginning,translate all the vertices with respect to the camera or viewers position…kind of like aligning the world with the viewers position…and then set the viewers vector to [0,0,0]… Thanks