@User: Metals 1 to 5 are used for long distance routes. Local interconnect is expressly forbidden for long distance routes (with an obscure and hard-to-implement rule stating that it must have an aspect ratio less than 10 on any length not contacting either up or down). The general convention in the standard cell libraries is that local interconnect and metal 1 on the power rails are doubled up and routed horizontally, so that makes the preferred directions metal 1 = horizontal, metal 2 = vertical, metal 3 = horizontal, metal 4 = vertical, and metal 5 = horizontal. 45 degree angles are used mostly in I/O pads and areas with high voltage, or for RF considerations like inductor coils. Mostly this is just due to the annoying painfulness of dealing with non-manhattan geometry generally. There are few DRC rules involving adjacent layers; most of those have to do with constructions like MiM capacitors.