The goal of this clinical trial is to assess the safety, tolerability, pharmacokinetics, and pharmacodynamics of once-weekly subcutaneous injections of MET233 in otherwise healthy adults with overweight or obesity. The trial will be conducted in three parts. Part A consists of single ascending dose (SAD) cohorts of MET233 or placebo. Part B consists of multiple ascending dose (MAD) cohorts, with participants treated with five once-weekly doses of MET233 or placebo. In Part C, participants will receive once-weekly doses of MET233 or placebo for 12 weeks, followed by a single higher, potential monthly dose.