The Dubno Magid zt”l explains the importance of Birchas Hamazon with a moshol:
There once was a widower who had an only son, whom he loved and doted on very much. He eventually remarried to a widow who had a daughter from her first marriage.
The husband was concerned that she would be busy taking care of her daughter and would not spend enough time caring for his son. At the same time, the wife was worried that her husband would only care about his son and would not care for her daughter. The truth was that they were both right – they both subconsciously cared more for their own child than for their stepchild, which led to some tension in the home.
When both the son and daughter came of age, the parents began to discuss shidduchim for them, and decided that the best idea would be for them to marry each other. After their marriage, the young couple cared for each other, while their parents continued to care for them. Since they all were concerned for the welfare of the new couple, they all were on the same page, and shalom bayis returned to the home. Thus, the original cause of strife between them became the cause of harmony amongst them.
The nimshol is as follows: Hashem created man with both a body – which desires gashmius – and a neshama – which desires ruchnius. Since the neshama is always striving for spiritual growth, while the body is always seeking physical pleasure, there is constant friction between them. The way to create harmony between them is when a person enjoys the earthly pleasure of food but uses his eating as means to connect to Hashem by reciting brachos before eating and Birchas Hamazon afterwards. Since both aspects of the person are working together, they are able to coexist peacefully.
