Is the Islamic murabaha currently practiced in banks permissible, which involves the bank paying a sum of money to the client in exchange for the bank purchasing shares, metals, or cars, provided that the amount is paid in monthly installments?

If the bank gives the customer a sum of money to be repaid with an increase, this is usury (riba) and not Islamic murabaha. Islamic murabaha is when the bank buys the commodity and then sells it to the customer in installments at a profit. It is permissible to appoint the bank as an agent to sell the commodity that the customer bought from it after taking possession of it, and to buy shares, metals, or cars with the price of that commodity.