Metromover. Free, no ticket, no tap. Three loops through downtown and Brickell, elevated one storey above the street, running from early morning to around 10pm daily. It reaches the bayfront museum park with PAMM and Frost Science, Bayside Marketplace, the Freedom Tower, Brickell City Centre, MiamiCentral station and the courthouse district. If you are staying downtown or in Brickell, this is your transport and you will not need much else within that footprint.
Metrorail. Two lines, elevated, running roughly north to south from Dadeland through Coconut Grove, Coral Gables' Douglas Road, Brickell and downtown up to Hialeah and Palmetto, with the Orange Line branching to Miami International Airport. Flat fare $2.25, daily cap around $5.65, paid by EASY Card, the transit app or contactless. It connects to the Metromover free at Government Center and Brickell. For an airport arrival staying downtown, this is a genuinely good option: train from MIA to Government Center, then the Metromover.
Metrobus. County-wide, comprehensive on paper, slow in practice, same $2.25 fare. Useful for specific corridors, particularly Biscayne Boulevard and the causeway routes into Miami Beach, and unrewarding as a general strategy.
The Miami Beach Trolley. A free, city-run circulator covering South Beach, Mid-Beach, North Beach and the Collins corridor. It is genuinely useful if you are based on the island and want to move a few dozen blocks without paying to park. Routes change, so check the current map rather than an old one.
MIA Mover. A free automated shuttle connecting Miami International Airport's terminals to the Miami Intermodal Center, where the rental car centre, Metrorail's Orange Line, Tri-Rail and the regional buses all are. If you are renting a car at MIA, this is the link you take to reach it.
Brightline. Higher-speed intercity rail from MiamiCentral downtown to Aventura, Fort Lauderdale, Boca Raton, West Palm Beach and on to Orlando. Fort Lauderdale is around 40 minutes, Orlando around three and a half hours. Advertised Miami to Orlando fares start around $39 on the cheapest tier and rise from there. MiamiCentral connects directly to the free Metromover and to Metrorail, which makes a car-free day trip north genuinely practical.