He probably was the one known as Baal in the Bible (although Baal seems to have been a more general name for Canaanite deities). The priests of Melkart had much political power in Tyre.
Melkart probably arrived in Tyre from its mother-city, Sidon, but he got renewed importance as the most important city deity during the reign of Hiram I, who built a large new temple for Melkart in the island section of Tyre, described by Herodotus and other Greeks. It contained the pair of symbolic pillars one 'of gold' the other of 'smaragdus'— often translated as 'emerald.' Hiram also installed the yearly celebration of the egersis, as the Greeks called it. It took place when the rains of Winter ended (in February-March), in which the god was burned, buried and resurrected, as a solar life-death-rebirth deity. Melkart was the Bull of the Sun, associated with the annual renewal of fertility. The fire was supposed to bring new life, an old theme in Phoenician mythology. The king himself had important ceremonial functions during this festival, and would hold a ritual marriage with a priestess of the queen, symbolizing the marriage of Melkart and Astarte. Sometimes Melkart was actually identified with the king, a habit that earned Tyre the wrath of the biblical prophets.