Chinese Astrology (the Chinese Zodiac) is an esoteric branch of Chinese Medicine. Its guiding principles have to do with the balance of yin and yang energies and the flow of life energy called chi. 

The Chinese zodiac follows Jupiter’s orbit around the sun, which takes about 11.8 years to complete. Each year has its own animal and element. Known as the Wu Xing, the five movements, or five phases, the elements (earth, metal, water, wood, and fire) represent the cycle of life and correspond to the seasons (spring, summer, transitional, fall, and winter). There are 12 animal zodiacs and each one is inherently connected to one of these five elements.

You can calculate your Chinese zodiac sign using the year you were born. The time of year you were born is also a factor. For example, if you were born in February, around the start of the new year, you may have very little of the element of that year because you were conceived and developing under the previous zodiac. 

The year 2021 is a Year of the Ox, which is connected to the Earth element (associated with winter and yin energy). But the year 2021 will be a metal year. So while the Earth element will always be part of the nature of the Ox sign, people who are born in 2021 will be Metal Ox or Golden Ox. Metal’s attributes are firmness, rigidity, persistence, strength, and determination. The metal person is controlling, ambitious, forceful, and slightly set in their ways, as metal is very strong. It’s important to note, though, that we hold all of the element’s energies within us, and they are constantly interacting with the influences of yin and yang. 

https://www.mindbodygreen.com/articles/chinese-new-year-2021