| M.a. Metal Co., Inc Laser, Bending, Welding, Stamping, Assembly · ISO 9001 | Columbus, IN | LaserBendingWeldingStampingAssembly | ISO 9001 |
| M's Machines Milling, Turning, Welding | Monona, IA | MillingTurningWelding | - |
| M&M Metals Inc. Bending, Laser, Welding | San Antonio, TX | BendingLaserWelding | - |
| Mac Cal Co Welding · ISO 13485 | San Jose, CA | Welding | ISO 13485 |
| Mac Smith Corp Milling, Turning, Laser, Waterjet, Bending, Welding, Stamping, Grinding | Gardena, CA | MillingTurningLaserWaterjetBendingWeldingStampingGrinding | - |
| Mac-Tech Turning, Bending, Laser, Welding | Milwaukee, WI | TurningBendingLaserWelding | - |
| Machine Repair & Design Milling, Turning, Waterjet, Welding, Finishing, Assembly · AS9100 | Sumner, WA | MillingTurningWaterjetWeldingFinishingAssembly | AS9100 |
| Machine Service Inc Welding · ISO 9001 | Green Bay, WI | Welding | ISO 9001 |
| Machine-Tech Services, L.L.C Milling, Turning, Welding | Broussard, LA | MillingTurningWelding | - |
| Machining Tech Milling, Turning, Waterjet, Welding, Stamping, EDM, Grinding | Hazle Township, PA | MillingTurningWaterjetWeldingStampingEDMGrinding | - |
| Machworks LLC Welding | Thomaston, GA | Welding | - |
| Mack Engineering Corp Milling, Turning, Swiss, Welding, Stamping · ISO 9001 | Minneapolis, MN | MillingTurningSwissWeldingStamping | ISO 9001 |
| Magna Machine & Tool Co Inc Milling, Turning, Waterjet, Welding, EDM, Grinding | New Castle, IN | MillingTurningWaterjetWeldingEDMGrinding | - |
| Magna Tool Inc Milling, Turning, Welding · AS9100 | Cypress, CA | MillingTurningWelding | AS9100 |
| Majestic Metals by Fathom Manufacturing Milling, Turning, Bending, Laser, Welding, Waterjet, EDM, Casting, Metal AM · ISO 9001, AS9100, ITAR, ISO 13485 | Denver, CO | MillingTurningBendingLaserWeldingWaterjetEDMCastingMetal AM | ISO 9001, AS9100, ITAR, ISO 13485 |
| Manda Machine Co Milling, Turning, Laser, Welding, Waterjet, EDM · ISO 9001, AS9100 | Dallas, TX | MillingTurningLaserWeldingWaterjetEDM | ISO 9001, AS9100 |
| 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 |
| Mark One Metal Works Turning, Bending, Welding | Sparks, NV | TurningBendingWelding | - |
| Marton Precision MF Milling, Turning, Waterjet, Welding, EDM, Finishing · ISO 9001, AS9100, ITAR | Fullerton, CA | MillingTurningWaterjetWeldingEDMFinishing | ISO 9001, AS9100, ITAR |
| Marvel Manufacturing Milling, Turning, Swiss, Welding, EDM, Grinding, Finishing | Lewiston, ID | MillingTurningSwissWeldingEDMGrindingFinishing | - |
| Marzilli Machine Co Milling, Turning, Welding · ISO 9001, ITAR | Seekonk, MA | MillingTurningWelding | ISO 9001, ITAR |
| 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 Precision Machining Milling, Welding · ISO 9001, AS9100 | Santa Clara, CA | MillingWelding | ISO 9001, AS9100 |
| Max Machine Milling, Turning, Laser, Waterjet, Welding, Grinding, Finishing · ISO 9001 | Elizabethtown, PA | MillingTurningLaserWaterjetWeldingGrindingFinishing | ISO 9001 |
| MaxFab Milling, Laser, Punching, Bending, Welding, Stamping, Finishing, Assembly | Madison, AL | MillingLaserPunchingBendingWeldingStampingFinishingAssembly | - |
| Maxsteel Fabrication, LLC Milling, Turning, Laser, Welding, Finishing | Paris, TN | MillingTurningLaserWeldingFinishing | - |
| Maynard Inc Bending, Welding · ISO 9001, AS9100, ITAR, NADCAP | Fayetteville, AR | BendingWelding | ISO 9001, AS9100, ITAR, NADCAP |
| MC Engineering Inc Welding | Mesa, AZ | Welding | - |
| McCallin Steel Storage Systems, Inc Milling, Punching, Welding, Finishing | Commerce City, CO | MillingPunchingWeldingFinishing | - |
| McClintic R-D-M, Inc Milling, Turning, Waterjet, Welding | Albuquerque, NM | MillingTurningWaterjetWelding | - |
| McKenna Metal Bending, Laser, Welding, Waterjet | Portland, OR | BendingLaserWeldingWaterjet | - |
| Mdi Manufacturing Inc Milling, Turning, Welding, Grinding, Assembly · ISO 9001 | Lakewood, NJ | MillingTurningWeldingGrindingAssembly | ISO 9001 |
| Mega Machine Shop Inc Milling, Turning, Welding | Tumwater, WA | MillingTurningWelding | - |
| Melton Sheet Metal Bending, Welding | Fresno, CA | BendingWelding | - |
| Menze Precision Machining, LLC Milling, Turning, Bending, Welding, EDM, Grinding, Finishing | Winter Haven, FL | MillingTurningBendingWeldingEDMGrindingFinishing | - |
| Meridian Manufacturing Inc Milling, Turning, Laser, Welding, EDM, Grinding, Finishing | Ballston Spa, NY | MillingTurningLaserWeldingEDMGrindingFinishing | - |
| 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 | - |
| Metal Arts LLC Welding | Wichita, KS | Welding | - |
| Metal Components LLC Turning, Waterjet, Bending, Welding, Finishing, Assembly · ISO 9001 | Grand Rapids, MI | TurningWaterjetBendingWeldingFinishingAssembly | ISO 9001 |
| Metal Fusion Inc Milling, Turning, Welding, Grinding | Redwood City, CA | MillingTurningWeldingGrinding | - |
| Metal Man Milling, Waterjet, Bending, Welding | Watertown, NY | MillingWaterjetBendingWelding | - |
| Metal Master Inc Milling, Welding | San Diego, CA | MillingWelding | - |
| Metal Masterminds Laser, Waterjet, Punching, Bending, Welding, Stamping | Fountain Valley, CA | LaserWaterjetPunchingBendingWeldingStamping | - |
| Metal Tech Inc Laser, Welding | Gulfport, MS | LaserWelding | - |
| Metal Works Precision Machine and Tool, Inc Milling, Turning, Welding | Tucson, AZ | MillingTurningWelding | - |