The objective of Metta meditation is to cultivate goodwill and compassion towards all living being. Usually, it begins with the meditator generating compassion and love towards themselves, their loved ones, friends, teachers, strangers and enemies.
It is a good way to calm down a distraught mind bacause it is an antidote against anger. A person who has cultivated Metta will not be easily angered and can quickly subdue anger that arises. This person will be more caring, more loving, love more and more unconditionally.
A person who has a lot of Metta will be happier because s/he sees no need in harbouring illwill or hostility. At the same time, people around a Metta-ful person will feel comfortable and happier too. Radiating Metta contributes to a world of love, peace and happiness.