Your question: What is the purpose..... Zinc and Phosphorous are used in oil formulations as anti-wear compounds. Moly is uses in some oils as anti-wear. Calcium and Magnesium are detergent/dispersants to keep the engine clean and avoid filter plugging and deposits.
Most other metals found in the analisis are wear metals unless you use leaded gasoline. Then lead - sometimes more than 1000 ppm - is coming from the gasoline.
If you can handle spanish, I have a lot of information and a table of where the wear particles prabably come from on
www.widman.biz