| M&M Machining, Inc Milling, Turning, Welding, Finishing | Ventura, CA | MillingTurningWeldingFinishing | - |
| Machine & Tool Manufacturing Company Milling, Laser, Waterjet, Welding, Finishing | Adel, GA | MillingLaserWaterjetWeldingFinishing | - |
| Machine Repair & Design Milling, Turning, Waterjet, Welding, Finishing, Assembly · AS9100 | Sumner, WA | MillingTurningWaterjetWeldingFinishingAssembly | AS9100 |
| Machine Tool Engineering Milling, Turning, Swiss, Laser, Waterjet, Stamping, EDM, Grinding, Finishing · ISO 9001, AS9100, NADCAP | Charles City, IA | MillingTurningSwissLaserWaterjetStampingEDMGrindingFinishing | ISO 9001, AS9100, NADCAP |
| Magna Machining, Inc Milling, Turning, Finishing | Richfield, NC | MillingTurningFinishing | - |
| Magnum Machine Inc Milling, Turning, Welding, Finishing · ITAR | Raymond, NH | MillingTurningWeldingFinishing | ITAR |
| Magnum Machining LLC Milling, Turning, Finishing | Richmond, IL | MillingTurningFinishing | - |
| Manderscheid, Inc Milling, Finishing · ITAR | Plano, TX | MillingFinishing | ITAR |
| Manor Tool & Manufacturing Co Milling, Laser, Waterjet, Bending, Welding, Stamping, EDM, Grinding, Finishing · ISO 9001, ITAR | Schiller Park, IL | MillingLaserWaterjetBendingWeldingStampingEDMGrindingFinishing | ISO 9001, ITAR |
| Manufacture.us Milling, Turning, Swiss, Laser, Finishing, Assembly | Doral, FL | MillingTurningSwissLaserFinishingAssembly | - |
| Manufacturing Solutions LLC Milling, Turning, Welding, Finishing | Tulsa, OK | MillingTurningWeldingFinishing | - |
| Mapp Technologies, L.L.C Milling, Welding, Grinding, Finishing · NADCAP, CMMC | Joplin, MO | MillingWeldingGrindingFinishing | NADCAP, CMMC |
| Marinette Machine LLC Turning, Welding, Grinding, Finishing | Marinette, WI | TurningWeldingGrindingFinishing | - |
| Maritech Machine Inc Milling, Turning, Waterjet, Welding, Grinding, Finishing · ISO 9001, AS9100 | Panama City, FL | MillingTurningWaterjetWeldingGrindingFinishing | ISO 9001, AS9100 |
| Mars Engineering Milling, Turning, Waterjet, EDM, Grinding, Finishing, Assembly | San Leandro, CA | MillingTurningWaterjetEDMGrindingFinishingAssembly | - |
| Marsam Metal Finishing Co Finishing, Assembly | New Britain, CT | FinishingAssembly | - |
| Marvel Manufacturing Milling, Turning, Swiss, Welding, EDM, Grinding, Finishing | Lewiston, ID | MillingTurningSwissWeldingEDMGrindingFinishing | - |
| Massie Mfg Inc Milling, Turning, Laser, Waterjet, Bending, Welding, Finishing · ITAR | Baraga, MI | MillingTurningLaserWaterjetBendingWeldingFinishing | ITAR |
| Masters Machine Company Milling, Turning, Swiss, Grinding, Finishing · ISO 9001, ITAR | Bristol, ME | MillingTurningSwissGrindingFinishing | ISO 9001, ITAR |
| MaxFab Milling, Laser, Punching, Bending, Welding, Stamping, Finishing, Assembly | Madison, AL | MillingLaserPunchingBendingWeldingStampingFinishingAssembly | - |
| Maxsteel Fabrication, LLC Milling, Turning, Laser, Welding, Finishing | Paris, TN | MillingTurningLaserWeldingFinishing | - |
| McCallin Steel Storage Systems, Inc Milling, Punching, Welding, Finishing | Commerce City, CO | MillingPunchingWeldingFinishing | - |
| McCormick Industries Inc Milling, Turning, Swiss, Welding, Grinding, Finishing, Assembly · ISO 9001 | Appleton, WI | MillingTurningSwissWeldingGrindingFinishingAssembly | ISO 9001 |
| Meridian Manufacturing Inc Milling, Turning, Laser, Welding, EDM, Grinding, Finishing | Ballston Spa, NY | MillingTurningLaserWeldingEDMGrindingFinishing | - |
| Merit Industries Milling, Turning, Laser, Waterjet, Welding, EDM, Grinding, Finishing · AS9100, ITAR, NADCAP, CMMC | Erie, PA | MillingTurningLaserWaterjetWeldingEDMGrindingFinishing | AS9100, ITAR, NADCAP, CMMC |
| Mesco Manufacturing Group LLC Milling, Laser, Welding, Finishing · ISO 9001 | Greensburg, IN | MillingLaserWeldingFinishing | ISO 9001 |
| Met International Trading Company, Inc Laser, Punching, Bending, Welding, Finishing | Houston, TX | LaserPunchingBendingWeldingFinishing | - |
| Meta-Tech Industries, Inc Milling, Turning, Welding, EDM, Finishing · ISO 9001 | Houston, TX | MillingTurningWeldingEDMFinishing | ISO 9001 |
| Metal Components LLC Turning, Waterjet, Bending, Welding, Finishing, Assembly · ISO 9001 | Grand Rapids, MI | TurningWaterjetBendingWeldingFinishingAssembly | ISO 9001 |
| Metal Essence Inc Milling, Turning, Swiss, Finishing, Assembly · ISO 9001, AS9100, ITAR | Longwood, FL | MillingTurningSwissFinishingAssembly | ISO 9001, AS9100, ITAR |
| Metalbuilt LLC Milling, Turning, Laser, Welding, Stamping, Finishing · ISO 9001, AS9100, IATF 16949 | Chesterfield, MI | MillingTurningLaserWeldingStampingFinishing | ISO 9001, AS9100, IATF 16949 |
| Metalcraft Industries, Inc Welding, Stamping, Finishing, Assembly · CMMC | Denver, CO | WeldingStampingFinishingAssembly | CMMC |
| Metalmasters Milling, Turning, Bending, Welding, Finishing | Brighton, CO | MillingTurningBendingWeldingFinishing | - |
| Metalquest Unlimited, Inc Milling, Turning, Finishing, Assembly | Hebron, NE | MillingTurningFinishingAssembly | - |
| MF Engineering Company, Inc Milling, Turning, Swiss, Welding, Grinding, Finishing · ISO 9001, NADCAP | Bristol, RI | MillingTurningSwissWeldingGrindingFinishing | ISO 9001, NADCAP |
| Micro-Tec, Inc Milling, Turning, Welding, EDM, Finishing · ISO 9001, AS9100 | Chatsworth, CA | MillingTurningWeldingEDMFinishing | ISO 9001, AS9100 |
| Mid-Continent Engineering, LLC Bending, Welding, Grinding, Finishing · ISO 9001, AS9100, ITAR | Minneapolis, MN | BendingWeldingGrindingFinishing | ISO 9001, AS9100, ITAR |
| Mikron Manufacturing Inc Milling, Turning, Laser, Punching, Bending, Welding, Finishing, Assembly · ISO 9001, ITAR | Colorado Springs, CO | MillingTurningLaserPunchingBendingWeldingFinishingAssembly | ISO 9001, ITAR |
| Millennium Metalcraft, Inc Milling, Laser, Bending, Welding, Finishing, Assembly · ISO 9001 | Fremont, CA | MillingLaserBendingWeldingFinishingAssembly | ISO 9001 |
| Milo Engineering Milling, Turning, Grinding, Finishing · ISO 9001 | Torrance, CA | MillingTurningGrindingFinishing | ISO 9001 |
| Mimic Manufacturing, LLC Welding, Finishing | Heavener, OK | WeldingFinishing | - |
| Miramar Metal Processing Inc Welding, Finishing · ITAR, NADCAP | San Diego, CA | WeldingFinishing | ITAR, NADCAP |
| MMG Corp Milling, Turning, Finishing, Assembly · ISO 9001 | Ontario, CA | MillingTurningFinishingAssembly | ISO 9001 |
| Modern Manufacturing & Engineering, Inc Milling, Turning, Swiss, Grinding, Finishing · ISO 9001, AS9100, ITAR, NADCAP | Brooklyn Park, MN | MillingTurningSwissGrindingFinishing | ISO 9001, AS9100, ITAR, NADCAP |
| Modus Advanced Milling, Waterjet, Finishing, Assembly · ISO 9001, AS9100, ITAR, CMMC | Carlsbad, CA | MillingWaterjetFinishingAssembly | ISO 9001, AS9100, ITAR, CMMC |
| Monsees Tool & Die Inc Milling, Turning, EDM, Grinding, Finishing | Rochester, NY | MillingTurningEDMGrindingFinishing | - |
| Moore Tool Company, Inc Stamping, Grinding, Finishing, Assembly · ISO 9001, AS9100 | Bridgeport, CT | StampingGrindingFinishingAssembly | ISO 9001, AS9100 |
| Moria Manufacturing LLC Milling, Turning, Finishing | Monona, WI | MillingTurningFinishing | - |
| Mountain CNC Milling, Turning, Waterjet, Welding, Grinding, Finishing, Assembly · ITAR, CMMC | Loveland, CO | MillingTurningWaterjetWeldingGrindingFinishingAssembly | ITAR, CMMC |
| Mountain Precision Tool Co, Inc Milling, Turning, Laser, Waterjet, Punching, Bending, Welding, EDM, Grinding, Finishing | Blacksburg, VA | MillingTurningLaserWaterjetPunchingBendingWeldingEDMGrindingFinishing | - |