Can you drive a 18 wheeler at the age 16?

No, you cannot. You cannot obtain a CDL (or state equivalent for vehicles of that class which are exempt from CDL requirements, such as registered farm vehicles) until you turn 18. Even then, it's very restrictive - you'd only be permitted to operate a commercial vehicle within the boundaries of your home state. To be able to transport interstate commerce, and/or obtain a hazardous materials endorsement, you must be 21. On top of that, most companies require prospective employees to be at least 23 years of age.