Using common words:
* Mighty Mountains
* Magnificent Monarch
* Marvelous Music
* Mysterious Maze
* Melodic Melodies
Using more creative words:
* Mischievous Magpie
* Mellifluous Moonbeams
* Marvellous Mermaid
* Magnificent Meteor
* Mystic Mermaid
You can also create your own alliterations! Just think of words that start with "M" and put them together in a creative way.