Countless eons ago, having made many offerings, Maitreya took bodhisattva vows from the Tathagata Great Power in front of many other buddhas. From that moment on he has led countless sentient beings to enlightenment, guiding them along the path of the three higher trainings of discipline, concentration and wisdom by means of the three vehicles: Shravakayana, Pratyekabuddhayana and Mahayana.
While practicing as a bodhisattva he specialized in the meditation on great love. He not only taught this path to others but also meditated upon it continuously himself, often stationing himself at the gate of a city and contemplating deeply on loving kindness. His meditation was so powerful that people passing by close enough to touch his feet would themselves receive the realization of great love. This greatly pleased the tathagatas of the ten directions, who rejoiced in his actions and predicted that in all his future lives as a bodhisattva and a buddha he would be known as “Love” [Skt: Maitreya; Tib: Jampa]. This is how he received his name.
In one of those lifetimes Maitreya was born as one of the thousand sons of a great king. This king wanted to know in which order his sons would become enlightened, so he put all their names into a bowl, meditated deeply for seven days while performing many ritual offerings, and then drew the names out of the bowl one by one. Maitreya’s name came out fifth, and the buddha of that age, the Tathagata Limitless Knowledge, predicted that Maitreya would be the fifth buddha of the present era, Shakyamuni being the fourth.
Eventually Maitreya advanced through all the levels of spiritual development, achieved the tenth and highest level of a bodhisattva, and afterwards became a fully enlightened buddha. Having reached this level of utmost perfection, he manifested in many different aspects in countless buddha fields; at present his particular abode is the pure land of Tushita, where he imparts Mahayana teachings to countless advanced bodhisattva disciples. It was here that he taught his five famous texts to the great Arya Asanga. Maitreya also gives many other teachings, in accordance with the needs of different disciples. He appears as countless spiritual masters throughout the ten directions of space, thereby leading innumerable beings along the path to full awakening.
Finally the time will come for Maitreya to appear as the fifth universal buddha of this world age and turn the wheel of Dharma for the benefit of all.
Source: FPMT by Lama Yeshe