I have a dictionary in which the word "bond" occurs as an entry four separate times and there are a combined multitude of entries for different meanings which the word can have, so I 'm not sure just where you want to begin. However, I can think of a couple of places to start:
1. I believe the very common idiomatic expression "his word is his bond" is basically a metaphorical expression. If you describe a man that way, you mean that when he says he'll do something or promises something then he will perform or deliver exactly as he has indicated--no other surety, bond, or written contract is needed (to ensure or enforce compliance) other than his own honesty and integrity.
2. "To bond" can be used in a more figurative sense than merely to cement or join two things together physically: When the two children met for the first time, they instantly bonded and remained friends for the rest of their lives. Here, there are no physical ties or cement but only emotional and affective bonds that reside in the feelings and trust the two children have for each other.
I hope the above is useful.