Salam alaykum brothers/sisters
I am going to talk about the role of Imams (S.A) in society;
The Imam is necessary for spiritual life of people to remain alive.
The Imam is like water in purity. God says in surah al-Furqan verse forty eight,
وَ اَنزَلنا مِنَ السَّماءِ ماءً طَهُورا
"...and We send down from the sky pure water".
Water is both pure and purifier. In the same way, the Imam is both in a high level of purity and can make others spiritually pure as well. It is narrated from Imam Ali saying,
وَ لَو قَد قَامَ قَائِمُنا ... لَذَهَبَتِ الشَّحنَاءُ مِن قُلُوبِ العِبادِ
"When our Upriser (Imam al-Mahdi) arises, the animosity will go away from the hearts of people."2
This narration points to spiritual purification of people that will be obtained with the help of the Imam.
Sources:
l.'Usul al-Kafi, v. 1, p. 25, hadith no. 1.
2. al-Khisal, v. 2, p. 626.