If you are on windows, what i suppose you need to do set the PATH like this:
SET PATH=%M2%
furthermore i assume you need to set your path to something like C:...\apache-maven-3.0.3\ cause this is the default folder for the windows archive. On the other i assume you need to add the path of maven to your and not set it to only maven so you setting should look like this:
SET PATH=%PATH%;%M2%