Most mechanics specialize in a particular field, such as auto body mechanics, diesel mechanics, air conditioning and refrigeration mechanics, auto mechanics, bicycle mechanics, boiler mechanics, race car mechanics, aircraft mechanics, and other areas. There are also mobile mechanics who work on heavy equipment that will come to you if there is an issue that must be resolved at the location of the machine.^[2]

A mechanic is typically certified by a trade association or regional government power. Mechanics may be separated into two classes based on the type of machines they work on, heavyweight and lightweight. Heavyweight work is on larger machines or heavy equipment, such as tractors, construction equipment, and trailers, while lightweight work is on smaller items, such as automobiles.

1. Automotive mechanics, also known as auto mechanics, specialize in repairing and maintaining automobiles, including cars, trucks, and motorcycles. They work on engines, transmissions, brakes, steering and suspension systems, and other mechanical components of vehicles.
2. Truck mechanics specialize in repairing and maintaining trucks, such as tractor units, box trucks, dump trucks and garbage trucks. They work on diesel engines, transmissions, air brakes, steering and suspension systems, and other mechanical components of trucks.
3. Aircraft mechanics, also known as aviation mechanics, specialize in repairing and maintaining aircraft, including planes and helicopters. They work on engines, landing gear, avionics, and other mechanical and electrical systems.^[3]
4. Marine mechanics specialize in repairing and maintaining boats and other watercraft. They work on engines, transmissions, propellers, steering systems, and other mechanical components of boats.^[4]
5. Industrial mechanics, also known as maintenance mechanics, work in industrial settings such as factories and manufacturing plants. They are responsible for maintaining and repairing machinery and equipment, including pumps, conveyors, and other mechanical systems.
6. Heavy equipment mechanics specialize in repairing and maintaining heavy equipment such as bulldozers, excavators, and cranes. They work on diesel engines, transmissions, hydraulic systems, and other mechanical components of heavy equipment.
7. Bicycle mechanics: Bicycle mechanics are tradesmen who specialize in repairing and maintaining bicycles. They work on frames, wheels, brakes, gears, and other mechanical components of bicycles.^[5]

Automotive mechanics have many trades within. Some may specialize in the electrical diagnosis, while others may specialize in the mechanical aspects. Other mechanical areas include: brakes and steering, suspension, automatic or manual transmission, engine repairs, auto body repairs, or diagnosing customer complaints.

Automotive mechanics require many years of training to become licensed. Countries like Canada have a governmental certification body that tests and maintains automotive mechanics' qualifications.^[6] The United States of America uses an organization that is called ASE.^[7] This organization provides independent testing of an automotive mechanic's skills with over 57 different tests that can be taken.