Bahrain is a small country and distances are short -- you can drive from one end of the main island to the other in under an hour. But public transport is limited, so having your own wheels helps.
Car rental is the most practical option for exploring beyond Manama. Roads are well-maintained, signage is in Arabic and English, and driving is on the right. Traffic in Manama can be congested during rush hours, but outside the capital it is manageable. International rental agencies operate at the airport and in the city. An international driving permit is recommended.
Taxis are plentiful in Manama and around the airport. Insist on the meter or agree on a fare before getting in -- overcharging tourists is not unknown. Ride-hailing apps like Uber and Careem operate throughout the country and are often the easiest option.
Buses run a limited network connecting Manama with other parts of the island. They are cheap but infrequent and not particularly convenient for visitors. The main bus terminal is in Manama near Bab al-Bahrain.
The King Fahad Causeway connects Bahrain to the Eastern Province of Saudi Arabia. The drive takes about 90 minutes including border formalities, which can be slow on weekends when Saudi visitors pour in. You will need a valid Saudi visa to cross.
Bahrain has no metro or rail system, though one has been discussed for years. For now, taxis and rental cars are how you get around.