Ajahn Dhammasiha explains 'Loving Kindness' meditation ('Mettā'). Loving Kindness is the intention of unconditional, non-judgemental goodwill to all conscious beings.
We start by generating this intention to just one being that we find most easy to feel sympathetic towards. Once the intention becomes strong in our mind, we notice a very pleasant feeling, a wholesome, uplifting emotion that is connected with the intention of goodwill. We build up that feeling, that emotion, until it becomes sufficiently stable that we can direct it to more and more beings, neutral and even difficult ones, until we extend limitless loving kindness to all beings without distinction, and throughout the whole universe.