The chemical reactions and pathways involving pectic arabinan, a polymer with an alpha-(1->5)-linked L-arabinofuranose (Araf) backbone that can be substituted with Araf-alpha-(1->2)-, Araf-alpha-(1->3)-, and/or Araf-alpha-(1->3)-Araf-alpha-(1->3)-side chains. Arabinan can be found as a side chain of the pectin rhamnogalacturonan I.