Inclusion Criteria:  Main inclusion criteria (all participants)  Age 60-79 years. Cardiovascular Risk Factors, Aging and Dementia (CAIDE) Risk Score ≥6 points. Cognitive performance at the mean level or slightly lower than expected for age according to local population norms based on the Montreal Cognitive Assessment (MoCA) test and the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) verbal learning test. Proficiency in the local language (English, Finnish or Swedish)  Inclusion criteria for metformin/placebo treatment (only for participants in the FINGER 2.0 multimodal lifestyle-based intervention arm)  No diagnosed diabetes or known contraindications to metformin treatment. Elevated adiposity (BMI≥25 kg/m2 OR waist circumference > 102 cm in men and > 88 cm in women) OR mildly impaired fasting glucose (6.1-6.9 mmol/l).  Exclusion Criteria:  Main exclusion criteria (all participants)  Dementia or substantial cognitive impairment (e.g., memory clinic referral needed as judged by the study physician). Current or past use of medications for Alzheimer's Disease or related diseases (e.g., cholinesterase inhibitors, memantine, aducanumab). Diminished decision-making capacity, not capable of consenting or completing study assessments, based on clinical judgement. Other known significant neurologic disease (including e.g., Parkinson's disease, Huntington's disease, normal pressure hydrocephalus, brain tumour, progressive, supranuclear palsy, seizure disorder, subdural hematoma, multiple sclerosis, or history of significant head trauma with persistent neurologic sequelae or known structural brain abnormalities). Any other condition affecting safe engagement in the intervention (e.g., malignant disease, major depression, symptomatic cardiovascular disease, revascularisation within the previous year). Severe loss of vision, hearing, or communicative ability; conditions preventing cooperation. Coincident participation in the active phase of another intervention trial. A member of the household already enrolled in the MET-FINGER trial  Exclusion criteria for metformin/placebo treatment (only for participants in the FINGER 2.0 multimodal lifestyle-based intervention group)  Use of metformin for any indication. History of intolerance to metformin used for any indication. Diabetes diagnosed or suspected at baseline (e.g., HbA1c≥6.5%, fasting glucose ≥7 mmol/l, or 2HPG≥11.1 mmol/l). Metformin contraindications, e.g., history/presence of known renal or liver disease, congestive heart failure, alcohol abuse, calculated Glomerular Filtration Rate<60 ml/min.