This is a randomized, placebo-controlled, double-blind study designed to investigate the safety, tolerability, PK and pharmacodynamic (PD) of single and multiple ascending subcutaneous (SC) doses of MET233 in otherwise healthy adult participants with obesity or overweight (body mass index \[BMI\] 27.0 kg/m2 to 38.0 kg/m2, inclusive for Parts A-C and BMI in Part D 30- 45.0 kg/m2 (inclusive).
* In Part A, participants will receive a single dose of MET233 at up to five dose levels.
* In Part B, participants will receive five weekly doses of MET233 at up to four dose levels.
* In Part C, participants will receive 12 weekly doses of MET233. These doses may include titration. For all cohorts in Part C, a 13th dose administered on Day 85 may be a monthly-equivalent dose to evaluate the potential for switching to a monthly dosing regimen.
* In Part D, participants will receive 12 once-weekly doses, followed by three monthly doses of MET233 or placebo.
