**Leave the breaker off and don’t keep resetting it.** The tripping indicates a fault, likely a short circuit. Before anyone touches the wiring, power must be shut off and verified absent with a suitable tester. [ESFI safety guidance](https://www.esfi.org/test-before-you-touch)

**Two black and two white ceiling wires aren’t enough information to determine the connections safely.** In older switch-loop wiring, a white wire can carry hot power instead of being neutral. Connecting all wires by color can therefore create a short.

One possible arrangement is a power-supply cable plus a cable carrying power to and from the switches. In that arrangement, one connection at the ceiling feeds the switches, while a separate wire returns switched power to the lamp. Your description does not establish which wire serves each purpose.

Once the wires are positively identified, the new fixture’s connections are:

| Fixture wire | Connects to |
|---|---|
| Black | Verified switched hot from the switches |
| White | Verified neutral |
| Green or bare | Verified equipment ground, with required fixture/box bonding |

The existing 3-way switches can continue controlling a fixture with just those three leads. Any splice supplying the switches must also be preserved.

The old fixture’s “little metal tab” does not establish how the ceiling wires should be grouped. **Because the original connections have been disturbed and the breaker now trips, have a qualified electrician trace the ceiling and switch wiring and check for damage before reconnecting it.** Don’t try alternate combinations to see which works.