What do the bird and serpent on the Mexican flag symbolizes?

The bird and serpent on the Mexican flag mean the Implication of the court of arms.

The beautiful flag of Mexico is a vertical tricolor of green, white, and red with the national coat of arms imposed in the middle of the white stripe. The meaning of the colors has changed over time, these three colors were chosen by Mexico following independence from the Spain. The figure of the coat of arms was most recently amended in 1968, but the complete design has been used since 1821 when the First Mexican National Flag was designed.

Red, white, and green are the colors of the national liberation army in Mexico. The emblem in the center of the flag, Mexico’s coat of arms, has been a significant figure in Mexican politics and culture for years, fording way back to when the city was named Tenochtitlan. 

The coat of arms that occupies a space on today’s Mexican flag represents a golden eagle, rested on a prickly pear cactus, gulping a rattlesnake. This is the Aztec saga that the god told the leader of the tribe, in his dream that when a bird was found perching on a cactus gorging a snake, they had found the site to start to make their cherished city.

Throughout history, the flag has evolved many a time. However, the coat of arms has had the same hallmarks everywhere: an eagle, clutching a serpent in its hook, is perched on top of a thorny pear cactus; the cactus dwells on a rock that stands above a lake. 

The real meanings of the symbols to the people of Tenochtitlan were all very diverse. The eagle was a symbol of the sun god Huitzilopochtli, this was very crucial as the Mexicans introduce themselves as the “People of the Sun”. The cactus described the island of Tenochtitlan (Mexico City was originally an island surrounded by vast water). And the snake signified wisdom and this animal to had powerful meanings with an alternative god.

When the Europeans later came to Mexico, it would come to signify the triumph of good over wrong (with the snake seldom representative of the viper in the Garden of Eden).

The first national flag was alike to the national flag that is used today, except the eagle was not clutching a serpent in his nails and a crown had been fastened to the head of the eagle to imply the Empire.

The second national flag was approved after the establishment of the first federal republic in 1823. The crown was removed from the eagle's head and a snake was placed in the eagle's right talon. 

The third national flag was that of the Second Mexican Empire. The ratio of the flag was changed from 4:7 to 1:2 and four eagles, which had crowns above their heads, were placed at each corner of the flag. 

The current national flag was adopted on September 16, 1968, and was confirmed by law on February 24, 1984. In this, the eagle was brought back to center but changed from a front-facing to a side-facing position.