Loving-kindness (Metta) meditation is a concentration practice which can be complementary to the mindfulness practice. It adds softness to the practice and helps cope with difficulties when mindfulness does not seem to work.
Metta, is a Pali (an ancient language similar to Sanskrit) term which literally means friendliness, the first of the four sublime states (brahmavihara) which also includes compassion (karuna), sympathetic joy (mudita) and equanimity (upekkha). It is unconditional love, with care, and without expectation. It has the quality of non-possessive and non-clinging (romantic love is not Loving-Kindness). It is gentle, non selective and has no barrier, just as the rain falling on all subjects on earth nourishing all it touches regardless of who or what is good or bad. Loving-Kindness is well-wishing thought towards all beings. It is usually compared to the love of a mother for her only child. It is helpful to reflect on some good quality of the Metta subject (the person you are about to send love to). You can think of a simple nice thing that this person has done for you or for someone else before evoking the intention of well-wishing for this person. It is important to feel Loving-Kindness in the heart and not just be reciting the words. Although one can start with words, eventually the feeling of love and connection will come.
One traditionally starts with forgiveness phrases, both asking for and forgiving: “if I have knowingly or unknowingly caused harm to anyone, I ask their forgiveness. If anyone has hurt me, I forgive them”. If you have difficulty with this, forgive just yourself or skip this part for now and try it later when loving-kindness has been established.
Begin the Loving-kindness by expressing it first to yourself. Reflecting on your good qualities, on happiness, and your right to be happy is far from being selfish: experiencing/acquiring Metta allows one to fully share it with others. Allow this feeling to pervade your entire being. If you have difficulty with yourself, begin with any one (or any object such as a pet or teddy bear) that is the easiest to connect with, then try yourself. Extend this feeling to a benefactor (such as a parent or teacher), a dear friend, a neutral person, and (later in the practice, if possible) ending with a difficult person while reflecting on some good quality this subject possesses. You can also radiate the Metta energy spatially outward to the people/beings in this neighborhood, town, state, country, world and the universe.
The four traditional phrases are
-"May I be free from harm…
-May I be well…
-May I be happy…
-May I live with ease”
or simply
“May I be well, safe and happy” or "May I be well, happy and peaceful".
Then substitute “I” for “you,” then eventually substitute “all beings” for “you.”
Silently repeat these (or your own phrases). You can synchronize the phrases with the breath. Example: "May I be safe" with the in-breath, "May I be well, happy and peaceful" with the out-breath. Be creative. Remember to relax and be comfortable. You can stay with just one category (like yourself), or two, for the entire period.
This practice can be done formally at the beginning or the end of a mindfulness sitting meditation, by itself, (using the attached audio below) or informally during the day whenever applicable/practical. It can be done also while walking back and forth (like in the formal mindful walking meditation) while reciting the phrases, if it is easier for you. You may not feel anything at first but please be patient. It is like turning on the air-conditioner in a hot room and coolness will come later. It might be helpful to gradually develop loving kindness, like turning on the light gradually with a dimmer switch, so that one would not be startled by the bright light or see too many junks (in the garage) at once.
*One can also mindfully observe the feeling of Metta (in the mind and body), seeing how it changes without holding on to it, thus leaving concept and observe ultimate reality, making this an insight practice instead of pure concentration practice as described above. (See "Concept and reality").