Lovingkindness and Compassion of the Buddha? In an effort to understand the concept of lovingkindness it would help me to see how the Buddha explicitly described lovingkindness and specific acts of his unconditional compassion. I've heard from secondary sources that he'd throw out his "net" of compassion to walk 200 miles to teach someone, but I'm looking for references to primary or well known secondary (e.g. Bhikku Bodhi, Analayo) sources, please.
You've asked about metta.

The deepest example of metta does not use the word metta.

In SN6.1, we hear that Brahmā Sahampati kneels and asks the Buddha to teach the Dhamma.


  Sir, let the Blessed One teach the Dhamma! Let the Holy One teach the Dhamma!


To which the Buddha humbly replied: 


  Thinking it would be troublesome, Brahmā, I did not teach the sophisticated, sublime Dhamma among humans.


The Buddha spent the rest of his life teaching. Now that is the very definition of metta.