אז ישיר Az Yashir, which is the most famous song in the world, was sung by Moshe. Moshe was called: עבד ה' an Eved Hashem, who was totally attached and constantly grateful to Hashem. Rashi says that Moshe was a Melech. A Melech is a symbol of Kavod, and Kavod is appreciation. By being M'kayem Kibud Av V’em, we are showing our appreciation to them for bringing us into this world. A: מורד במלכות rebel against the king is Chayav Missa, since a king is the epitome of Kavod. He has Kavod, and he deserves Kavod.
Dovid HaMelech used to spend half a night learning Torah and the other half he sang (Gemara) in appreciation of the Torah he learned during the first half. (R' Zundel of Salant Zatzal). Look how extreme he is in appreciating his own Torah; ½ a night of singing. This is a true Melech, and that’s why: דוד מלך ישראל חי וקיים Dovid lives on for eternity. If he would have built the Bais Hamikdash, then it would have been impossible to destroy it. A Melech loves and appreciates his life, with all the goodness that Hashem gives him, and he never stops singing!
על כל נשימה ונשימה תהלל קה We have to thank Hashem for every single breath of air. Every inch of his life is precious to him, and he never stops thanking and singing. (By the way, those who love life - sing and praise, thank, appreciate, and respect themselves and others. They are builders, and not destroyers like Hamas.)
