[AngelicaDeAlquezar]

Both "soportar" and "aguantar" are synonymous when they mean to bear the weight of something (literally or metaphorically), or to tolerate.

- Esta estructura no soporta/aguanta mucho peso.
This structure can't bear too much weight.

- No soporto/aguanto a Juan.
I can't stand Juan.

- Te entiendo. Siempre tienes que aguantar/soportar los abusos.
I empathize. You always have to bear the abuse.

- No me digas que no; mi corazón no lo soportaría/aguantaría.
Don't reject me; my heart wouldn't be able to take it.


They are not synonymous though, when the verb "aguantar" means to restrain or to contain:

- Aguanté las ganas de llorar para que no me vieran débil.
I held back the tears so they wouldn't see I was weak.

- Si el jinete no hubiera aguantado el caballo con las dos manos, me habría pisoteado.
If the rider wouldn't have had held the horse with both hands, it would have trampled me.

- ¿Cuánto aguantas la respiración bajo el agua?
How long can you hold your breath under the water?