In the Metta Bhavana practice we’re cultivating love, or friendliness, or lovingkindness.

Eventually we want to become like an emotional bonfire: a steady blaze of emotional warmth that will embrace any sentient being that we become aware of. This is an attainable goal for every human being. All it takes is time and some persistent effort.

The practice is in five stages. We cultivate Metta for:

• Ourselves
• A good friend
• A “neutral” person — someone we don’t have any strong feelings for
• A “difficult” person — someone we have conflicts with or feelings of ill will towards
• All sentient beings (ambitious, huh!)

You may notice that there’s a progression in the stages. It’s easiest for us to cultivate lovingkindness for ourselves and for our friends. It’s a bit more difficult to do this for people we don’t know well. And it really goes against the grain to cultivate lovingkindness for someone we’re in conflict with. Lastly, we cultivate lovingkindness for everyone in the world: i.e. all friends, people we don’t know, and people we’re in conflict with — plus ourselves of course.

We’ll learn these stages one at a time. We suggest that you practice one stage for a while before moving on to the others.

Source: http://www.wildmind.org