In the past, most rockets used RP-1, or Kerosene, in their first stage engine, however now many companies are using methane, in a metholox engine, for their fuel.
The benefits of methane over Kerosene include its ease of handling as a gas due to the warmer temperatures rockets experience, simpler and quicker combustion simulation, and a closer temperature to LOX.
Methane is also cheaper than Kerosene, however, the main deciding factor seems to be a variety of small benefits that add up to a meaningful overall benefit when considering the engineering of the whole rocket system.
The video referenced in the article goes into more details on each of the advantages and disadvantages of each fuel type and is linked in the text above.
