What is the ruling on using financial leverage in commodity trading (such as coffee and oil) through a brokerage firm if the leverage is non-obligatory and entails no fees or interest, taking into account that the company only charges a commission for buying and selling?

The intermediary company's condition that the client must trade through it to use leverage is considered a loan that draws benefit for the company, which is usury (riba). The fact that leverage is optional does not change the ruling on its use. However, if the client avoids leverage and ensures that the company's dealings are free from Sharia prohibitions, then there is no objection to dealing with it.