Metals are defined in the CMOS process.
Metal1 verticiale
Metal2 horizontal and so forth.
As we move in lower process technology, the rules regarding routing of metal in non defined direction becomes stringent.
for example you in 45nm technology you can route narrow metal in horizontal, also it can be routed only to small distance.
My question is why these stringent rules, what type of problem do they the pose to fabrication.
Previously, having consecutive metals in perpendicular directions has nothing to do with fabrication. It is a layout guideline to decrease the coupling between the lines but in the end nothing prevents you from routing them in parallel.
I have not still dabbled with 45nm but perhaps you can find your answer here