The development of Metta or Loving-Kindness along with Compassion, Joy and Equanimity make up the four ‘divine’ emotional states (aka Four Immeasurables, Four Divine Abidings, or Four Brahmaviharas) in Buddhism. Cultivating these 4 states creates less claustrophobia and more space within one’s being and helps one’s interactions in daily life. Below is the teaching (sutra) the Buddha gave on how to practice Metta. This version was found in Sharon Salzberg’s wonderful book “Loving-Kindness: The Revolutionary Art of Happiness”.
This is what should be done
By those who are skilled in goodness,
And who know the path of peace:
Let them be able and upright,
Straightforward and gentle in speech.
Humble and not conceited,
Contented and easily satisfied.
Unburdened with duties and frugal in their ways.
Peaceful and calm, and wise and skillful,
Not proud and demanding in nature.
Let them not do the slightest thing
That the wise would later reprove.
Wishing: in gladness and in safety,
May all beings be at ease.
Whatever living beings there may be;
Whether they are weak or strong, omitting none,
The great or the mighty, medium, short or small,
The seen and the unseen,
Those living near and far away,
Those born and to-be-born—
May all beings be at ease!
Let none deceive another,
Or despise any being in any state.
Let none through anger or ill-will
Wish harm upon another,
Even as a mother protects with her life
Her child, her only child,
So with a boundless heart
Should one cherish all living beings;
Radiating kindness over the entire world:
Spreading upwards to the skies,
And downwards to the depths;
Outward and unbounded,
Freed from hatred and ill-will
Whether standing or walking, seated or lying down,
Free from drowsiness,
One should sustain this recollection.
This is said to be the sublime abiding.
By not holding to fixed views,
The pure-hearted one, having clarity of vision,
Being freed from all sense desires,
Is not born again into this world.