| Mestamaster Oy | Information & communication | 2019 |
| Mestari Davidsson Oy | Manufacturing | 2025 |
| Mestarikettu Oy | Education | 2020 |
| Mestariluokka Helena ja Jukka Ahonen Oy | Education | 1991 |
| Mestaripalvelu Raka Oy | Construction | 2025 |
| Mestaripalvelut Appelgren Oy | Professional & scientific | 2019 |
| Mestaripojat Oy | Construction | 1994 |
| Mestariteos Oy | Information & communication | 2020 |
| Mestoil Films Ab | Information & communication | 2023 |
| Mesvest Oy | Wholesale & retail | 1993 |
| Met Cap Oy | Financial services | 2024 |
| MetaLogic Oy | Information & communication | 2001 |
| Metabox Oy | Professional & scientific | 2020 |
| Metacode Oy | Information & communication | 2023 |
| Metacore Games Oy | Manufacturing | 2015 |
| Metafora Intelligence Oy | Professional & scientific | 2026 |
| MetalPro Rakennus Oy | Manufacturing | 2025 |
| Metalheim Oy | Professional & scientific | 2008 |
| Metalli HoldCo Oy | Financial services | 2026 |
| Metalli Klaavu Ky | Manufacturing | 1992 |
| Metalli24 OY | Wholesale & retail | 2024 |
| Metallikonepaja Oy | Manufacturing | 1933 |
| Metallinkylä Property Holding Oy | Financial services | 2021 |
| Metallinkylä Property Oy | Real estate | 2014 |
| Metallisorvaamo Artikkelituotanto Oy | Professional & scientific | 1994 |
| Metallitae Oy. Vesi- ja lämpöjohtopalvelu | Construction | 1945 |
| Metallitalo Oy | Wholesale & retail | 1941 |
| Metals One Exploration Oy | Mining & quarrying | 2021 |
| Metaneira Oy | Real estate | 2000 |
| Metaphysics Oy | Professional & scientific | 2014 |
| Metaplay Oy | Information & communication | 2019 |
| Metar Consulting Oy | Professional & scientific | 2009 |
| Metaspace Oy | Information & communication | 2021 |
| Metaterveys Oy | Health & social care | 2022 |
| Metaverse | Information & communication | 2021 |
| Metaversumi Oy | Professional & scientific | 2021 |
| Metavisio Oy | Professional & scientific | 1998 |
| MeteoExpert Oy | Professional & scientific | 2011 |
| Meteor Capital Oy AB | Financial services | 2026 |
| Meterion Oy | Wholesale & retail | 2023 |
| Mether Capital Ab | Financial services | 2022 |
| Method Putkisto Finland Oy | Arts & recreation | 1991 |
| Metic Global Oy | Administrative & support | 2024 |
| Metis Consulting Group Oy | Professional & scientific | 2023 |
| Metis Oy | Information & communication | 1987 |
| Metka Media Oy | Professional & scientific | 2022 |
| Metodica Oy | Professional & scientific | 2018 |
| Metores Oy | Wholesale & retail | 2009 |
| Metria Oncology Oy | Professional & scientific | 2025 |
| Metrify.io Oy | Information & communication | 2012 |
| Metrikum Oy | Wholesale & retail | 2026 |
| Metro Investments Oy | Real estate | 1994 |
| Metro Taxi Ky | Transport & logistics | 1962 |
| Metro-Mutanen Oy | Wholesale & retail | 2020 |
| MetroWorx International Oy | Wholesale & retail | 2023 |
| Metroauto Group Oy | Wholesale & retail | 1985 |
| Metroauto Oy | Wholesale & retail | 1989 |
| Metroc Oy | Information & communication | 2019 |
| Metropol House Oy | Real estate | 2001 |
| MetropoliLab Oy | Professional & scientific | 2010 |
| Metropolia Ammattikorkeakoulu Oy | Education | 2007 |
| Metropolia opiskelijakunnan opiskelijapalvelut Oy | Hospitality | 2003 |
| Metropolin Siivouspalvelu Oy | Administrative & support | 2025 |
| Metropolitan Genius Loci Taksipalvelu avoin yhtiö | Transport & logistics | 1998 |
| Metrovisio, Koskinen kommandiittiyhtiö | Wholesale & retail | 1965 |
| Metry Oy | Professional & scientific | 2007 |
| Metso Accounting Oy | Professional & scientific | 2024 |
| Metso Silva Oy | Agriculture & fishing | 2024 |
| Metsä - Lasse Oy | Construction | 2025 |
| Metsä ja Puu I Ky | Financial services | 2021 |
| Metsä ja Puu II Ky | Financial services | 2021 |
| Metsä ja Puu III Ky | Financial services | 2021 |
| Metsä ja Puu Oy | Financial services | 2021 |
| Metsä ja kiinteistö Häkkinen & Andersson Oy | Real estate | 2022 |
| Metsä-Juntulan Energiapuisto GP Oy | Energy | 2023 |
| Metsä-Juntulan Energiapuisto Ky | Energy | 2023 |
| MetsäForce Oy | Agriculture & fishing | 2025 |
| Metsäalan opiskelijatiimi Oy | Agriculture & fishing | 2018 |
| Metsähallitus Metsätalous Oy | Agriculture & fishing | 2016 |
| Metsähuoltokeskus Oy | Agriculture & fishing | 2024 |
| Metsäkuva-arkisto Ky | Arts & recreation | 1982 |
| Metsälamminkangas Wind Oy | Energy | 2019 |
| Metsälän Autohuolto Oy | Other services | 1991 |
| Metsälän Putkitarvike Oy | Construction | 2001 |
| Metsälän Rengas Oy | Wholesale & retail | 2014 |
| Metsämassi Oy | Real estate | 2016 |
| Metsämood Oy | Wholesale & retail | 2021 |
| Metsänhoitoyhdistysten Palvelu MHYP Oy | Professional & scientific | 2002 |
| Metsänhumina Oy | Financial services | 2006 |
| Metsäpalvelu Arvometsä Oy | Agriculture & fishing | 2013 |
| Metsäperuna Oy | Agriculture & fishing | 2021 |
| Metsäranta Dent Oy | Health & social care | 2026 |
| Metsäsuunnittelu Halonen Oy | Agriculture & fishing | 2012 |
| Metsätapiola Property Oy | Real estate | 2020 |
| Metsätoimisto Häme & Liimatainen Oy Ab | Agriculture & fishing | 2024 |
| Metsätuokio Oy | Administrative & support | 2021 |
| Metsäviestintä Oy | Administrative & support | 1924 |
| Metsävilla Oy | Professional & scientific | 2006 |
| Metsäylioppilaiden Kuusikauppa K-116 avoin yhtiö | Wholesale & retail | 2025 |
| Metsäylioppilaiden Kuusikauppa K-117 avoin yhtiö | Wholesale & retail | 2026 |