What is the significance of knowing about the angels?

The significance of knowing the angel is basically for human beings to know that all of their deeds are being recorded, their thought are being monitored. This would help them to reflect before acting, because it is acting hastily that we fall into sin. [1] Prophet Muhammad (ﷺ) said that, “deliberate and careful action is from Allah and haste is from shaitaan.” [2]

References:

[1] Explanation of the World of Noble Angels, Dr. Bilal Philips (audio)

[2] Tirmidhi, vol 4, Hadith 2012 classed as Daeef (weak) by Sheikh Albani

Narrated By Sahl bin Sa’d who said that the Prophet (ﷺ)  said: “Haste comes from Satan” ( Sunan Tirmidhi, Book 16, Hadith 1555, classed as Hasan (fair) by Sheikh Albani