Guided Meditation on Mettā: Unconditional Good Will to All Beings - Ajahn Dhammasiha
Mettā is the intention of unconditional good will to everyone, non-judgemental loving kindness to all living beings. We use the formula: "May you be happy and at ease!" and repeat it silently in our mind, just like a mantra.
However, the words are only meant as a technique to arouse the feeling, the emotion of unconditional friedliness to all conscious beings. The main task in the beginning is simply to get that emotion, that feeling going in our heart.
Once we feel what the words of our mantra mean, then we can quite easily direct this emotion to more and more beings, radiating in all directions, and imagine that our good will extends throughout the universe, suffusing all beings with our loving kindness.