I think you may be talking about the BT'X anime.
B't X is set on an alternate Earth, where a faction known as the Machine Empire rules a significant large piece of land known as "The Area" in the Gobi Desert. The Machine Empire invests highly in scientific advancements and schools children from an early age to become striving scientists. Mechanical engineering have culminated in the creation of cyborgs and most recently mechanical beasts, powered by human blood, the Bt. The series mostly takes place in the Machine Empire, but also on Kamui island, where the main characters were born. An island that was created from a crashed meteor and contains a piece of a sun, far underground.
A B't (pronounced "beat") is the ultimate form of mecha designed for fighting - the B stands for Brain, Blood, Bravery and Battler. They have different forms and powers, usually based on mythological creatures. The B't's source of power is a device called BreakHeart, which is fueled by human blood. Once the BreakHeart is inserted into the B't's body, it creates a link between the blood donor and the B't. A B't is also outfitted with the Guard System, which protects its donor from various dangers and environment changes, such as volcanic heat, the crushing pressures beneath the ocean, or even the depths of space. However, the donor must be in physical contact with his or her B't for the system to work for them. Teppei is able to manifest a suit of protective armor called Battle Gear through use of the Messiah Fist. This has the additional benefit of activating the usually dormant wings on X's sides, enabling him to reach even greater degrees of speed and mobility.
Was kind of popular here in Argentina as well.