If a timing belt on 93 Geo Metro 1.0L breaks will it cause further engine damage?

Yes, a broken timing belt on a 1993 Geo Metro 1.0L will almost certainly cause significant engine damage. Unlike interference engines, where pistons and valves collide directly, the Geo Metro 1.0L engine is an *interference* engine. This means that when the timing belt breaks, the pistons can hit the valves, bending or breaking them. This will require a major engine repair, likely involving replacing bent valves, possibly a head gasket, and potentially other related components.