| M&M Metals Inc. Bending, Laser, Welding | San Antonio, TX | BendingLaserWelding | - |
| Mac Products, Inc Milling, Waterjet, Bending, Welding, Assembly · ISO 9001 | Kearny, NJ | MillingWaterjetBendingWeldingAssembly | ISO 9001 |
| Mac Smith Corp Milling, Turning, Laser, Waterjet, Bending, Welding, Stamping, Grinding | Gardena, CA | MillingTurningLaserWaterjetBendingWeldingStampingGrinding | - |
| Mac-Tech Turning, Bending, Laser, Welding | Milwaukee, WI | TurningBendingLaserWelding | - |
| Mach3 Machining Milling, Turning, Welding · ISO 9001 | Cuyahoga Falls, OH | MillingTurningWelding | ISO 9001 |
| Machine & Tool Manufacturing Company Milling, Laser, Waterjet, Welding, Finishing | Adel, GA | MillingLaserWaterjetWeldingFinishing | - |
| Machining Systems Corporation Milling, Turning, Welding, Grinding, Finishing · ISO 9001 | Crestwood, IL | MillingTurningWeldingGrindingFinishing | ISO 9001 |
| Machinists Inc Milling, Turning, Laser, Welding, EDM, Grinding · ISO 9001, ITAR | Seattle, WA | MillingTurningLaserWeldingEDMGrinding | ISO 9001, ITAR |
| Machintek Co Milling, Welding | Fairfield, OH | MillingWelding | - |
| Machworks LLC Welding | Thomaston, GA | Welding | - |
| Magnolia Machine Company Milling, Turning, Welding, EDM, Grinding | Auburndale, FL | MillingTurningWeldingEDMGrinding | - |
| Magnum Machine Inc Milling, Turning, Welding, Finishing · ITAR | Raymond, NH | MillingTurningWeldingFinishing | ITAR |
| Mannon Metal Works LLC Welding, Forging | Lebanon, MO | WeldingForging | - |
| Manor Tool & Manufacturing Co Milling, Laser, Waterjet, Bending, Welding, Stamping, EDM, Grinding, Finishing · ISO 9001, ITAR | Schiller Park, IL | MillingLaserWaterjetBendingWeldingStampingEDMGrindingFinishing | ISO 9001, ITAR |
| Maria Custom Sheet Metal Bending, Welding | Englewood, CO | BendingWelding | - |
| Maritech Machine Inc Milling, Turning, Waterjet, Welding, Grinding, Finishing · ISO 9001, AS9100 | Panama City, FL | MillingTurningWaterjetWeldingGrindingFinishing | ISO 9001, AS9100 |
| Mark One Metal Works Turning, Bending, Welding | Sparks, NV | TurningBendingWelding | - |
| Mass Precision Inc Welding, Assembly · ISO 9001, ISO 13485 | San Jose, CA | WeldingAssembly | ISO 9001, ISO 13485 |
| Massie Mfg Inc Milling, Turning, Laser, Waterjet, Bending, Welding, Finishing · ITAR | Baraga, MI | MillingTurningLaserWaterjetBendingWeldingFinishing | ITAR |
| Master Machine LLC Milling, Turning, Welding · ISO 9001 | Chattanooga, TN | MillingTurningWelding | ISO 9001 |
| Master Metal Products Co Bending, Welding | San Jose, CA | BendingWelding | - |
| Master Tool & Manufacturing Inc Turning, Bending, Welding, EDM, Grinding · ISO 9001, ITAR | Hiawatha, IA | TurningBendingWeldingEDMGrinding | ISO 9001, ITAR |
| Matern Metal Works, Inc Punching, Bending, Welding | Mansfield, OH | PunchingBendingWelding | - |
| Matrix Metalworks LLC Milling, Welding · ISO 9001 | Sugar Land, TX | MillingWelding | ISO 9001 |
| McAlpin Industries Inc. Milling, Bending, Laser, Welding, Stamping | Rochester, NY | MillingBendingLaserWeldingStamping | - |
| McClintic R-D-M, Inc Milling, Turning, Waterjet, Welding | Albuquerque, NM | MillingTurningWaterjetWelding | - |
| McGinley Manufacturing Milling, Turning, Swiss, Welding, EDM · ISO 13485 | Glenrock, WY | MillingTurningSwissWeldingEDM | ISO 13485 |
| McKenna Metal Bending, Laser, Welding, Waterjet | Portland, OR | BendingLaserWeldingWaterjet | - |
| McKiney Manufacturing Milling, Turning, Laser, Waterjet, Bending, Welding | Mitchell, NE | MillingTurningLaserWaterjetBendingWelding | - |
| MCW Certified Welding Ltd Punching, Bending, Welding | Delta, OH | PunchingBendingWelding | - |
| Mecca Design & Production Welding | Dallas, TX | Welding | - |
| Mega Machine Shop Inc Milling, Turning, Welding | Tumwater, WA | MillingTurningWelding | - |
| Megla Manufacturing, Inc. Milling, Bending, Laser, Welding, Waterjet | National City, CA | MillingBendingLaserWeldingWaterjet | - |
| Melting Point Metalworks LLC Laser, Bending, Welding | Brownsburg, IN | LaserBendingWelding | - |
| Memac Industries Inc Milling, Turning, Welding, Grinding | Lancaster, OH | MillingTurningWeldingGrinding | - |
| Menco LLC Welding, Assembly | Wallace, MI | WeldingAssembly | - |
| Mercury Machining Co Milling, Turning, Welding, Grinding | Pensacola, FL | MillingTurningWeldingGrinding | - |
| Metal Arts LLC Welding | Wichita, KS | Welding | - |
| Metal Master Inc Milling, Welding | San Diego, CA | MillingWelding | - |
| Metal Masterminds Laser, Waterjet, Punching, Bending, Welding, Stamping | Fountain Valley, CA | LaserWaterjetPunchingBendingWeldingStamping | - |
| Metal Pro, Inc. Milling, Bending, Welding | Phoenix, AZ | MillingBendingWelding | - |
| Metal Workz L.L.C Milling, Turning, Laser, Bending, Welding, Finishing | Albany, KY | MillingTurningLaserBendingWeldingFinishing | - |
| Metalcraft Creative Bending, Laser, Welding | Birmingham, AL | BendingLaserWelding | - |
| Metalcraft Inc Bending, Laser, Welding | Boise, ID | BendingLaserWelding | - |
| Metalcraft Services Of Tampa, LLC. Bending, Welding, Waterjet, Stamping | Tampa, FL | BendingWeldingWaterjetStamping | - |
| MetalMania Bending, Laser, Welding | Brooklyn, NY | BendingLaserWelding | - |
| Metalmasters Milling, Turning, Bending, Welding, Finishing | Brighton, CO | MillingTurningBendingWeldingFinishing | - |
| Metalogic Industries LLC Milling, Turning, Swiss, Laser, Welding, EDM, Grinding | Southbridge, MA | MillingTurningSwissLaserWeldingEDMGrinding | - |
| Metco Metal Fab. Bending, Laser, Welding | Chattanooga, TN | BendingLaserWelding | - |
| Meyer Tool & Manufacturing, Inc Milling, Turning, Welding · ITAR | Oak Lawn, IL | MillingTurningWelding | ITAR |