Maimonides Principal #3 – God has no Form

Does god had a physical form? Is there an accurate visual representation of god?  How does god reveal himself to us?  What is special about the 'angel' (messenger) of Malakh Adonai, the angel that has god's name?  What is the rabbinical commentary regarding Metatron?  Is  the Messiah, another form of how god's manifests himself to us?