Physical commodities hiring process

Hi all. I am a student based in the US interested in physical commodities trading and want to work for a trading house once graduated. However, I am just a little confused on the hiring process for these houses, and I can't find any alumni on linkedin that work at these companies to ask for help unfortunately. For junior summer internships, does recruitment also begin in sophomore year winter as it does for banking? Also, I have been told that a lot of the metal and energy traders have off-term internships/internships during all 4 seasons, yet on their websites, I haven't been able to find any mention of these programs. Is there another place that I should be looking/are these only available upon emailing the hiring team? Cheers