I suggest not using the term "guardian angel"... That puts a lot of expectations and weight on the angels. Angels aren't meant to protect and "guard" you from evil. They are simply to help you on your life path. The proper term would be "Mentor" angel... As they teach you how to live life to it's fullest and through your specific path.
It is a literal law in Heaven that an angel cannot show their true form. Their true form would be too much for the human mind to bear, and cause instances of insanity. Instead, they appear in a form that in familiar to us; animals or humanoids. Many archangels will not show their wings, as they are not prideful. They are modest, and they don't want to act as though they are higher than humans.
First, learn whatever you can about Metatron. Search the internet by googling his name, and then take notes. Don't just search for Metatron. Search for things related to her name. Such as more information on plants associated with him, or where this angel stems from.
Here is a bit of information to get you started; Metatron's name literally means "Little Yahweh" or "Little God" and it is recognized that he was originally the prophet Enoch when he was a human. God had Enoch ascend into the ranks of angels after his work on Earth was complete.