Access to the Metropolitan Lounge in Chicago is no longer offered to Business Class passengers free of charge. There is a $25 charge for passengers holding a BC ticket for admittance. If I read the policies correctly for Chicago, even the $25 will not get you access with a coach ticket.

However, this doesn't apply to you on the outbound trip. Passengers holding same day sleeper tickets are entitled to use the Metropolitan Lounge, arriving or departing.