Technically, yes, almost any modern phone and SIM will connect abroad; practically, the question is what it costs and whether your home carrier's roaming agreement covers the destination well. Roaming works through partnerships with local networks, so coverage is usually fine in cities, but you may be limited to whichever partner network your carrier uses, occasionally with slower speeds or spotty rural service compared to local SIMs.
The cost side is where plans diverge wildly. Some carriers include generous international roaming in their plans for certain regions, others sell reasonable daily or weekly roaming passes, and some still charge pay-as-you-go rates that can turn a week of casual use into a shocking bill, with data being the main culprit.
Before flying, check three things in your carrier's app: whether your destination is covered, what roaming actually costs or whether a pass exists, and that roaming is enabled on your line.